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The Crime of Aggression under the Rome Statute of the International Criminal Court: (4 chapter)

The Crime of Aggression under the Rome Statute of the International Criminal Court
Carrie McDougall
2013, Cambridge University Press
Online ISBN: 9780511894589
Hardback ISBN: 9781107011090

Chapter 4

4 The elevation of acts of aggression to the State act element of the crime of aggression

As noted at the outset of Chapter 3, to amount to the State act element of
the crime of aggression under Article 8bis (1), an act of aggression must
by its character, gravity and scale, constitute a manifest violation of the
Charter of the United Nations. This chapter will analyse this qualifying
threshold in an attempt to provide meaning to it. A number of criticisms
associated with the definition will be rebuffed, particularly that the
definition violates the nullum crimen sine lege principle and that the
definition has given a green light to ‘lesser violations’ of the UN
Charter. At the same time, it will be demonstrated that the definition
of the State act element of the crime of aggression under the Rome
Statute is inconsistent with the crime’s customary definition; and that it
will require the judges of the ICC to resolve controversies associated
with unclear rules under the jus ad bellum. The chapter will finally
consider the grounds for excluding criminal responsibility under
Article 31 of the Statute in relation to the crime.

An act of aggression that by its character, gravity and
scale constitutes a manifest violation of the Charter
of the United Nations

Chapter 1 outlined the fact that the incorporation of a qualifying thresh-
old was the tool used by the SWGCA to bridge the definitional divide.
Those States previously opposed to the employment of the 3314
Definition were persuaded to accept its use on the basis that the qual-
ifying threshold would limit the ambit of that definition. The ‘manifest
violation’ threshold was preferred by a majority over any explicit refer-
ence to a requirement that a use of force amount to a war of aggression
(which was seen as anachronistic in the twenty-first century) or that a
use of force have the object or result of the annexation or occupation of
territory (viewed as being overly restrictive), and over terms such as a
‘serious’ or ‘flagrant’ violation (viewed as inadequate and unclear).
Several commentators have criticised the threshold on the basis that
the meaning of a ‘manifest violation’ is itself not clear.1 The ambiguity
surrounding the threshold was a particular concern of the US when it
rejoined the negotiating table. In his intervention in Kampala, US State
Department Legal Adviser, Harold Koh, noted that the US was ‘con-
cerned that the apparent consensus on the wording of Article 8bis
marks sharp disagreement on particular points regarding the meaning
of that language’.2 It is, however, evident from interventions made by
States during meetings of the SWGCA that the threshold was intended,
at least by some, to exclude two types of acts from the jurisdiction of the
Court: acts of insufficient seriousness and acts of questionable legal
status.3 The former is perhaps less controversial. An interpretation
requiring acts to meet a certain level of gravity is clearly consistent
with the understanding of the meaning of acts of aggression under the
jus ad bellum and with the traditional understanding of the crime, and is
supported by earlier alternative threshold proposals that employed
explicit references to seriousness, gravity and largeness-of-scale.4
A number of States (including, in particular, Germany) consistently
maintained during the SWGCA’s negotiations that a threshold was also
necessary to ensure that uses of armed violence of questionable legal
status were also not criminalised.5 SWGCA meeting reports do not
describe this position well. For example, the June 2006 and January
2007 Reports refer to the threshold’s role in relation to the exclusion
of ‘borderline’ cases.6 Other reports fail to mention an alternative inter-
pretation at all, focusing exclusively on considerations of seriousness.7
This trend was remedied in June 2008, when Germany, in consultation
with Australia, successfully proposed an amendment to the draft June
2008 Report of the SWGCA.8 In the context of the Elements of the crime
of aggression, the SWGCA’s June 2009 Report also states that the man-
ifest violation qualification ‘was relevant to determine whether the
Court had jurisdiction and would exclude situations that could fall
within a legal grey area, but was without prejudice to other legal
avenues that the victim State might wish to pursue, such as a ruling
by the International Court of Justice on the act of aggression’.9 Several
commentators who participated in the negotiations have also observed
that the threshold is intended to serve the purpose of excluding, in
addition to acts of insufficient seriousness, uses of force the legality of
which is the subject of genuine debate.10 It thus seems clear that the
intent of at least some States was that the reference to ‘manifest viola-
tion’ in Article 8bis (1) requires not only that an act of aggression meet a
certain level of seriousness, but also that the act of aggression constitute
an unarguable legal violation of the UN Charter.
Whether this intention has been adequately captured by the language
employed in Article 8bis (1) is, however, open to debate. The meaning of
the term ‘manifest’ is not obvious. Little guidance is provided in the
Elements of the crime. Element 5 simply repeats the language of Article
8bis (1). Paragraph (3) of the Special Introduction to the Elements of the
crime states that ‘[t]he term “manifest” is an objective qualification’.
This is useful in that it makes it clear that assessments as to whether the
threshold has been reached are independent of the opinions of the
actors involved,11 but it sheds little light on the meaning of the term.
In an Understanding proposed during the Review Conference, the US
attempted to make use of the definition of a ‘manifest violation’ found
in Article 46 of the VCLT relating to violations of internal law regarding
competence to conclude treaties that invalidate a State’s ratification of,
or accession to, a treaty. That definition provides that ‘[a] violation is
manifest if it would be objectively evident to any State conducting
itself in the matter in accordance with normal practice and in good
faith’. The Understanding was rejected by States in Kampala but in all
likelihood because it was linked in the US’ proposal to an exception
relating to humanitarian interventions, discussed in Chapter 3. As
such, it is unlikely to be interpreted as a rejection of the definition per
se and, despite the fact that it was ultimately not reflected in the
Understandings, one can foresee that the VCLT definition might have
some persuasive value for the judges of the ICC.
More important, however, are the factors that the Article instructs
the Court to consider in making a determination as to whether the
manifest threshold has been reached. Gravity and scale seem to be
clearly relevant to considerations of seriousness. It is difficult to see,
however, how these terms are relevant to the question of the legality of
a use of force, as neither concept is ordinarily employed in order to
determine whether or not Article 2(4) of the Charter has been breached.
The reference to the ‘character’ of an act of aggression is more obtuse.12
It could be read as a reference to types of acts or a requirement of
evidence of mala fides.13 There is, however, no evidence available to
support an assertion that either interpretation was intended by the
SWGCA. The list of qualifying acts that follows the chapeau in Article
8bis (2) militates against an interpretation that the means by which force
is carried out is relevant to determining whether the manifest threshold
has been breached. And the SWGCA clearly steered away from any
object or purpose requirement in rejecting both the traditional defini-
tion of crimes against peace, and the German attempt to translate the
definition of ‘wars of aggression’ into a twenty-first century crime.14
The better view, therefore, seems to be that the reference to ‘character’
is related to the requirement that an incontrovertible breach of Article
2(4) be established.15
This raises the question of the relationship between character, gravity
and scale. Heinsch argues that the use of the conjunctive ‘and’ in the
definition indicates that all three components have to be fulfilled.16
Understanding 7 adopted at the Review Conference addresses this
issue. It states:
It is understood that in establishing whether an act of aggression constitutes a
manifest violation of the Charter of the United Nations, the three components
of character, gravity and scale must be sufficient to justify a ‘manifest’ determi-
nation. No one component can be significant enough to satisfy the manifest
standard by itself.
The question begged by this Understanding is whether all three fac-
tors must point to a manifest determination (as suggested by the first
sentence), or whether the satisfaction of two of these factors would
justify this conclusion (as suggested by the second). The question is an
important one. Presume, for example, that State A sends a trio of
commandos into the territory of State B (without consent or UN author-
isation), who execute the President of State B by the firing of a single
bullet. Arguably such a use of force would satisfy the gravity and char-
acter tests, but it would be questionable as to whether the ‘scale’ com-
ponent of the manifest violation threshold had been met.17
Some guidance is provided by the drafting history of the Understanding.
The language originally proposed by the US read:
It is understood that in determining whether an act is manifest, all three
components of character, gravity, and scale must be sufficient to justify a
‘manifest’ determination. Satisfaction of one criterion could not by itself be
sufficiently severe to meet the ‘manifest’ standard.
This language clearly suggests that all three factors must point to a
manifest determination. The US language was modified by the focal
point for the negotiations of the Understandings to read:
It is understood that in establishing whether an act of aggression constitutes a
manifest violation of the Charter of the United Nations, each of the three
components of character, gravity and scale must independently be sufficient
to justify a ‘manifest’ determination.18
The focal point’s formulation made it even clearer that the satisfac-
tion of all three criteria was required. During informal consultations,
however, the Canadian Delegation tabled modifications to the focal
point’s draft that resulted in the text adopted. The rationale provided
by Canada was that the threshold should be met by a use of force that
was ‘almost manifestly illegal with respect to one component, but
definitely manifestly illegal with respect to the other two compo-
nents’.19 The US said it could agree with the Canadian formulation
provided a second sentence was added (‘[n]o one component can be
significant enough to satisfy the manifest standard by itself’).
In an article jointly written with others, Claus Kress, focal point for
the Understandings’ negotiations, has written that:
The idea behind this sentence was to exclude the determination of manifest
illegality in a case where one component is most prominently present, but the
other two not at all. It was thought that use of the word ‘and’ in the formulation
of the threshold requirement in draft art 8 bis (1) excluded a determination of
manifest illegality in such a case and that the understanding should properly
reflect this fact.20
This accords with what seemed to be the understanding of the room
during the negotiations. As such, it seems that a strong argument can be
made that the satisfaction of two of the three components would be
sufficient to allow the Court to conclude that a use of force amounted to
a manifest violation of the Charter. Of course, such a conclusion should
not be taken to suggest that the satisfaction of two components should
automatically lead to a finding that the threshold has been met. As Kress
and von Holtzendorff have said:
To state that ‘no one component can be significant enough . . .’ is different from
stating that the Court must make a determination of ‘manifest illegality’ when-
ever two of the components are present. On the contrary, the first sentence of
the Understandings makes it plain that the Court must always look at all three
components, although they need not all be present to the same degree.21
As such, while the drafting is far from satisfactory, a good argument can
be made that the manifest violation threshold requires acts of aggres-
sion to both be of a particular seriousness and obviously unlawful. To
reach a determination as to whether this threshold has been met, the
Court will need to consider whether the combination of character,
gravity and scale indicate a serious and unlawful act.

Nullum crimen sine lege and the prohibition of analogy

Article 22 of the Rome Statute, in relevant part, states that:
1. A person shall not be criminally responsible under this Statute unless
the conduct in question constitutes, at the time it takes place, a crime
within the jurisdiction of the Court.
2. The definition of a crime shall be strictly construed and shall not be
extended by analogy. In case of ambiguity, the definition shall be
interpreted in favour of the person being investigated, prosecuted or
Article 22 thus covers not only the nullum crimen sine lege principle, but
also the related prohibition of extension by analogy. While interpreta-
tion by analogy can take different forms and Article 22(2) does not
specify which is prohibited,22 it appears clear that the Statute’s drafters
intended ‘to debar the imposition of criminal responsibility in respect
of substantially new crimes’.23 It is important in this context to note,
however, that the rule does not bar the use of analogy for the purpose of
interpretation: analogy ‘remains a valid and indeed necessary tool with
which to construe the meaning of the Statute’.24
The importance of ‘the principle of legality’ was referred to often
during the negotiations of the SWGCA. Despite this, the ASP decided to
employ agreed language that has long been acknowledged as exceedingly
ambiguous, and new language that is equally so – particularly in relation
to the manifest violation threshold. Could the employment of vague
and ill-defined terms result in the Court ruling that cases are inadmissible
or that accused persons are not guilty because their conduct cannot
unarguably be said to fall within the definition of the crime?
If the manifest violation threshold is interpreted as requiring uses of
force to be evidently illegal, as I have suggested it should be (and which
Article 22(2) suggests it must be), this would appear to overcome any
potential concerns associated with Article 22(1) in so far as the thresh-
old applies to illegality. There would appear to be no grounds upon
which it could be argued that a use of force that amounts to an act of
aggression that is particularly serious in terms of gravity and scale, is
not ‘a crime within the jurisdiction of the court’ if it is also indisputably
unlawful. Looked at in reverse, if there is a query as to whether a use of
force is lawful or not, it will not meet the threshold built into Article
8bis (1), meaning that a defendant can argue that a substantive element
of the crime cannot be satisfied, making reliance on Article 22(1)
That said, it is eminently foreseeable that the question of the meaning
of the second sentence of Article 22(2) may receive quite a workout in
future trials. Judicial interpretation will be needed to fill in the contours
of the definition of an act of aggression, as well as the manifest violation
threshold and the indicia of character, gravity and scale. For example, it
may have been established that uses of force must meet a certain
threshold of seriousness in terms of gravity and scale (which itself
may refer to the geographic breadth, intensity or duration of a use of
force, or a combination of all three) in order to qualify as the State act
element of the crime of aggression. Where, however, is the dividing line
between acts captured by the definition, and those excluded, to be
drawn? The SWGCA spoke only of acts of insufficient seriousness and
acts that were ‘borderline’ – border incidents being one of the few
factual examples I can recall ever having been cited during the debates.
Should this be understood as meaning that only de minimis violations of
the prohibition of the use of force are excluded? The individual ele-
ments of the crime (the planning, preparation, initiation or execution,
by a person in a position effectively to exercise control over or to direct
the political or military action of a State) contemplate relatively large-
scale events that actually require planning and preparation. This might
be an accident of the blind incorporation of the individual elements of a
crime that was focused on wars of aggression, but be that as it may the
individual conduct elements indicate that a de minimis interpretation
would be too narrow. But once we abandon the concept of de minimis,
what can be relied upon to divine the dividing line? Would a violation of
airspace coupled with the dropping of a single bomb that causes mini-
mal property damage and the deaths of fewer than 10 people be con-
sidered a manifest violation? What about the dropping of multiple
bombs that cause substantial property damage of no strategic military
value and no deaths? The dropping of multiple bombs that cause some
property damage and the deaths of 100 people? And what of low-level
but prolonged border skirmishes that result in several deaths a week
over a period of months or years?
The Court has been given very little guidance as to where to draw the
line in the sand. As such, while there is arguably a core of prohibited
conduct that will likely satisfy the definition of the State act element of
the crime of aggression on any reading (for example, an unprovoked
and unauthorised land and air military campaign of one State against
another accompanied by the armed forces of the first State that acts as
occupier of the second State causing extensive property damage and
substantial loss of life), it is highly likely that in more difficult cases the
Prosecutor and the Court will have no choice but to read the definition
in favour of accused persons under Article 22(2).

The most serious crimes of concern to the international
community as a whole

During the definitional debates in the SWGCA, suggestions were made
to delete the threshold clause, delegations arguing that ‘any act of
aggression would constitute a manifest violation of the Charter of the
United Nations, and that the definition should not exclude any acts of
aggression’.25 In this context, Daniel Nsereko, judge of the ICC and one-
time adviser in the Ugandan delegation to the SWGCA, suggests that the
criminalisation of only grave violations of the prohibition may implic-
itly condone lesser violations.26 His argument is that the exemption of
lesser violations will ‘encourage leaders of powerful States to launch
repeated, short, sharp armed attacks on less powerful states with
impunity’.27 In addition he contends that ‘small scale armed attacks
often spark off large-scale wars’,28 clearly implying that a narrow defi-
nition would fail to capitalise to the maximum extent possible on the
potential deterrent effect of the crime. In light of these comments, it is
anticipated that some will criticise the manifest violation threshold’s
likely exclusion of prohibited uses of inter-State armed violence.
In response, I would contend that a decision not to criminalise lesser
violations of the prohibition is not equivalent to the toleration of such
acts. A failure to criminalise certain forms of inter-State armed violence
has no effect on their illegal status under the jus ad bellum. To draw a
parallel: not all breaches of the Geneva Conventions were considered by
participants at the Rome Conference to amount to war crimes, yet it has
not been suggested that as a result any of the Convention provisions
have lost their status under international humanitarian law (IHL) as
binding treaty obligations.29
Paulus acknowledges that, though not all violations of IHL are crimes,
IHL is binding, but worries that:
when one sees how some state representatives handled the Nuclear Weapons
opinion of the ICJ or the ICTY Prosecutor report on the Kosovo war as justifica-
tion for what states were doing anyway, the confidence that non-criminal
violations of the jus ad bellum would still maintain the opprobrium of illegality
after they were sorted out from criminalisation is very modest . . . in the absence
of prosecution by the Court, states can easily view such abstention as an unjus-
tified bill of clean health. Thus, in the end, criminalisation may lead to the
unintended consequence of rendering the use of force easier rather than sanc-
tioning it more effectively.30
Paulus’ concerns seem to be overstated. First, it is a mischaracterisa-
tion to claim that States generally misunderstand the complexities of
the decisions to which Paulus refers. There is a significant difference
between politics and law, which Paulus has conflated. Second, for any
number of reasons other than the restricted definition (lack of jurisdic-
tion to try a particular accused, inability to enforce an arrest warrant
against a particular defendant, the operation of Article 16, the require-
ment that the Prosecutor focus on the most serious crimes) the ICC will
only ever consider a small percentage of violations of the prohibition of
the use of force. To suggest that those unlawful uses of force not labelled
criminal will be sanctioned suggests that other entities in the interna-
tional arena are also restricted to an examination of uses of force that
meet the Rome Statute’s definition. Of course in fact, regardless of crim-
inalisation, the Security Council will continue to be able to pursue meas-
ures under Articles 41 and 42 of the Charter in response to violations of
the prohibition, the General Assembly will be able to adopt resolutions
condemning such force, victim States will be able to bring complaints
before the ICJ seeking compensation on the basis of State responsibility
where the Court has jurisdiction, and there will be much motivation for
the victim State and its supporters to cry foul. The criminalisation of
certain prohibited uses of force adds another means of enforcing interna-
tional law – it does not detract from anything existing.
Nsereko’s concern as to the potential for small-scale attacks to spark
wider conflicts appears, moreover, to be misplaced, premised as it is on
a definition that would allow only the first use of armed force to be
criminalised. While the principle of priority was a key characteristic of
the 3314 definitional debates, it featured very little in the context of the
SWGCA’s negotiations and cannot be found in Article 8bis. As such, the
leader of any State that deliberately instigates an international armed
conflict by engaging in frontier incidents could readily be held account-
able for subsequent conduct or a course of conduct under Article 8bis (1),
even if the frontier incident in isolation would not attract individual
criminal responsibility.
Paramount in this context is Article 5(1) of the Rome Statute, which
provides that: ‘[t]he jurisdiction of the Court shall be limited to the most
serious crimes of concern to the international community as a whole’. It
might be contended that these words are merely a reference to the need
for the Prosecutor to exercise discretion in selecting individual cases for
investigation and prosecution, or a limit in relation to the type of
individual cases that might properly be heard by the Court. Certainly
under Article 15(2), the Prosecutor is obliged, in relation to proprio motu
investigations, to analyse the ‘seriousness’ of information received. To
this end, the Prosecutor has developed Criteria for Selection of Situations
and Cases, which, presuming a case is jurisdictionally admissible, makes
gravity the key selection criterion.31 Moreover, under Article 17(1)(d) of
the Rome Statute a case will be inadmissible if it ‘is not of sufficient
gravity to justify further action by the Court’. Thus the Statute clearly
requires the subject crimes of individual cases to be characterised as
‘serious’ before the Court may properly exercise jurisdiction over them.
This requirement, however, is a separate one. The correct interpreta-
tion of Article 5(1) is that the four crimes over which the Court has
jurisdiction are designated as the most serious crimes of concern to the
international community as a whole. This interpretation is consistent
with other references to the phrase found in the Statute. Notably,
Article 1 provides that:
An International Criminal Court (‘the Court’) is hereby established. It shall be a
permanent institution and shall have the power to exercise its jurisdiction over
persons for the most serious crimes of international concern, as referred to in this
Statute . . .32
As made clear by the emphasised words, the most serious crimes of
international concern can only be genocide, crimes against humanity,
war crimes and the crime of aggression, given that individual crimes
that might be the subject of an investigation or prosecution are not
‘referred to’ in the Statute per se. This interpretation is supported by the
́paratoires, which contain numerous expressions of State opin-
travaux pre
ion that the jurisdiction of the Court should be limited to ‘the most
serious crimes of concern to the international community, namely,
genocide, war crimes, crimes against humanity and the crime of
The preservation of the integrity of Article 5(1), therefore, required
the definition of the State act element of the crime of aggression to be
restricted in its application to unlawful uses of inter-State armed
violence that are so serious that they are comparable to genocide,
crimes against humanity and war crimes. This view was not lost on
States during the crime’s negotiations: one of the arguments advanced
in favour of the threshold was that not all of the acts enumerated in the
3314 Definition could be considered the ‘most serious crimes of concern
to the international community as a whole’.34
The key question then is not whether it was appropriate to exclude
certain uses of force but whether the definition of the crime of aggres-
sion under the Statute indeed restricts the Court’s jurisdiction to the
most serious crimes of concern. I would argue that this requires, at the
very least, a recognition of the fact that not all violations of Article 2(4)
of the Charter, or the customary prohibition, amount to the State act
element of the crime of aggression. Understanding 6, and particularly
the manifest violation threshold, are squarely aimed at limiting the
definition of the State act element of the crime of aggression to the
most serious violations of the Charter (measured in terms of gravity,
scale and consequences). That said, the means by which this aim has
been pursued are somewhat clumsy. As a result, the benchmark set is
subject to differing interpretations.
This has been amplified by some of the contradictions inherent in the
definition. It is difficult to see how certain of the illustrative acts listed
in Article 8bis (2), particularly those found in sub-paragraphs (e) and (f),
could form the basis of an act of aggression that meets this threshold
test. The inclusion of these acts in the illustrative list could be inter-
preted by the Court as a mere accident of history and the product of the
ASP’s reluctance to abandon agreed language. Alternatively, consistent
with conventions of interpretation that instruct courts to give meaning
to each word, let alone paragraph, of a treaty, the inclusion of the
conduct found in sub-paragraphs (e) and (f) could lead the Court to the
view that meeting the threshold is not an overly onerous task. Thus for
multiple reasons it is entirely possible that the bar could be set too high
or too low by a Court that is provided with little guidance under the
Of course a discussion of the seriousness of uses of force begs the
question of how seriousness and insufficient gravity in the context of
Articles 8bis (1) and 17(1)(d) should be interpreted. Are death and
destruction the primary measuring sticks, or are consequences of seri-
ous geopolitical concern also counted? The reference to scale in Article
8bis (1) might suggest the former, but the term ‘gravity’ as it appears in
both Article 8bis (1) and 17(1)(d) could be read as also encompassing the
latter. From a policy point of view it might be noted that geopolitical
consequences could be extremely severe and are clearly a large part of
the rationale for the prohibition of the use of force on which the crime
of aggression is based. On the other hand, it might be asked whether
the Court is equipped to evaluate international relations, and indeed
whether such action would be appropriate. This said, for all of the
reputational risks it might entail, there would seem to be little basis
from a literal, teleological or intent interpretive point of view to exclude
such factors from the consideration of the Court.

Inconsistency with customary international law

It could be suggested that the ASP was free to legislate rather than codify
the definition of the crime of aggression. Consistency with customary
international law, however, was a key concern of the drafters of the
Rome Statute.35 Several States made explicit interventions during the
Rome Conference to state that in their opinion:
the crimes to fall within the jurisdiction of the Court should be defined . . . on
the basis of generally accepted norms of customary international law. It was
not the task of the conference to legislate or progressively develop international
In addition, many States cited consistency, or inconsistency, with
customary international law as the primary reason why certain
proposed definitions were, or were not, acceptable to them.37 An analy-
sis of the definitions of crimes under the Statute, moreover, reveals that
they are generally consistent with customary international law.38
As Meron asserts: ‘[d]elegations filled in some gaps in Rome, but this
took place in the interstices of rules, not on the core of the rules, and
only on the margins of precisely delineating crimes against humanity
and war crimes’39. That the same definitional methodology should have
been applied to the crime of aggression makes sense, firstly, on the basis
of consistency.
Perhaps more importantly, Broomhall has compellingly argued that:
As a matter of fairness, the need to determine the customary nature of Statute
crimes arises from the fact that the Court may be called upon to exercise its
jurisdiction retroactively with respect to crimes allegedly committed on the
territory or by the nationals of non-States Parties in the cases of Security Council
referral under article 13 para. b or of a declaration [of] ad hoc acceptance of ICC
jurisdiction under article 12 para. 3 of the Statute. The only legitimate basis for
establishing the criminal responsibility of individuals would presumably – in
the absence of relevant national criminal prohibitions at the time of the alleged
conduct – be that of customary international law.40
A definition, moreover, that has crystallised into customary interna-
tional law has, by definition, the broad support of the international
community. A grounding in custom thus would also, at least in theory,
provide a basis for the requisite support needed for provisions relating
to the crime of aggression to come into force. Similarly, a custom-based
definition is likely to help ensure that there is ongoing support for the
investigation and prosecution of crimes of aggression.41 In sum, there
are good reasons for why we might assess the definition of the crime of
aggression under Article 8bis (1) against the customary definition of the
Is there then a customary equivalent to the crime of aggression? What
conduct does it prohibit?
Firstly, by way of background, it is important to consider the
Nuremberg and Tokyo definitions of the crime. I have argued else-
where42 that a close study of the factual findings of the IMT and IMTFE
judgments reveals that the term ‘war of aggression’ includes:
(i) war with the object of the occupation or conquest of the territory of
another State or part thereof;
(ii) war declared in support of a third party’s war of aggression; and
(iii) war with the object of disabling another State’s capacity to provide
assistance to (a) third State(s) victim of a war of aggression initiated by
the aggressor.
I further have argued that, while the second branch of the State act
element of crimes against peace under the Tribunal’s constitutive
instruments (wars in violation of international (law,) treaties, agree-
ments and assurances) was treated as superfluous by the Tribunals,
they did not question its legitimacy as a definition of the State act
element of the crime. Finally, as widely noted elsewhere, Control
Council Law No. 10 expanded the definition of crimes against peace to
include ‘invasions’.
In the early days of the United Nations there was an immediate effort
to consolidate and build upon the legacy of the Nuremberg and Tokyo
judgments. Peace treaties signed with Italy,43 Roumania,44 Bulgaria,45
Finland46 and Hungary47 in 1947 required those countries to ‘take all
the necessary steps to ensure the apprehension and surrender for trial’
of, inter alia, ‘persons accused of having committed, ordered or
abetted . . . crimes against peace’. The 1951 Convention Relating to the
Status of Refugees provides that the provisions of the Convention shall
not apply to any persons with respect to whom there are serious reasons
for considering that he or she has committed a crime against peace.48
Domestic constitutions and criminal codes promulgated in the years
immediately following World War II incorporated references to the
crime. Article 26(1) of the German Basic Law of 1949 states that:
Acts tending to and undertaken with intent to disturb the peaceful relations
between nations, especially to prepare for a war of aggression, shall be uncon-
stitutional. They shall be made a criminal offence.49
Article 93 of Japan’s amended 1907 Penal Code provides that: ‘[a]
person who prepares or plots to wage war privately upon a foreign
state shall be punished with imprisonment’.50 Article II of the Chinese
Law of 1946 identified as war criminals any alien who violated interna-
tional law by participating in ‘an aggression’ or unlawful war against
the Republic of China.51 The Greek Constitutional Act 73/1945,52 the
Danish Law of 12 July 1946 on the Punishment of War Criminals,53
the Polish Law Concerning Trials of War Criminals,54 and the United
States Law and Practice Concerning Trials of War Criminals by Military
Commissions, Military Government Courts and Military Tribunals55
also provided for the prosecution of crimes against peace.
On 11 December 1946 the GA affirmed the principles of international
law recognised by the Nuremberg Charter and Judgment under
Resolution 95(I) without articulating what those principles were.56
The ILC was given the job of formulating the principles of international
law recognised in the IMT’s Charter and judgment and to indicate the
place of those principles in a draft Code of Offences against the Peace
and Security of Mankind.57 By 1950, the ILC had agreed on the
‘Nuremberg Principles’. Principle VI (a) confirmed that crimes against
peace are ‘punishable as crimes under international law’ and defined
the crime in terms essentially identical to the IMT Charter.58 The ILC,
however, made no comment on the status of the crime under interna-
tional law. After a lengthy debate, the Commission concluded that since
the Nuremberg Principles had already been affirmed by the General
Assembly, the task entrusted to the Commission was not to express any
appreciation of the Principles as principles of international law, but
merely to formulate them without any indication as to their authority.59
Perhaps as a result, the authority of the Nuremberg Principles and the
effect of Resolution 95(I) have subsequently been the subject of much
debate. It is unclear whether, in affirming the principles, the Assembly
believed it was lending moral weight to generally recognised rules of
customary international law, or whether it was attempting to establish
the place of the principles in international law.60 Similarly, it is unclear
why the Assembly believed it was necessary to formulate principles that
it had already affirmed.61 Pompe recognises the uncertainty in the Sixth
Committee as to ‘the conformity of the principles of the Nuremberg
Tribunal with general international law, and, even more . . . an uncer-
tainty as to the consequences of a formal and binding acceptance of
these principles as binding law’.62 This was partly the result of criticism
of the Nuremberg trial, but also a result of changes in international
relations, particularly growing tensions between the Permanent Five.63
Overall, it would seem that the World War II trials were unlikely in
and of themselves to have created instant custom. Some of the rules that
were applied in the trials no doubt belonged to customary international
law before 1945. On the other hand, it seems quite clear that crimes
against peace were invented by the Allies and were not part of custom-
ary law at that time. As such, even if the General Assembly believed it
was lending moral weight to existing customary international law in
adopting Resolution 95(I), it could only have had this effect in relation
to some of the principles it affirmed – and certainly not in relation to the
existence or content of crimes against peace. Nonetheless, Resolutions
95(I) and Principle VI (a) of the Nuremberg Principles, together with
Resolution 177(II) and the inclusion of modern equivalents of crimes
against peace in the 1951 Draft Code of Offences against the Peace and
Security of Mankind, do serve to reflect a general approval of the
Nuremberg Charter and judgment.64 The GA resolutions and the pos-
itive comments of governments received in relation to the 1951 Draft
Code can more specifically serve as evidence of State practice and opinio
juris, capable of contributing to the formation of a customary rule.
During the years Member States were debating the definition of
aggression in the 3314 definitional process, the US adopted its Armed
Forces Field Manual, which lists ‘crimes against peace’ as a ‘crime under
international law’.65 Sweden adopted its Penal Code in 1962, section 2
of Chapter 19 of which states that:
A person who by violent means or foreign aid causes a danger of the Realm being
involved in war or other hostilities, shall, unless it is high treason, be sentenced
for instigating war to imprisonment for at least two and at most eight years.66
In 1968, section 80 was inserted into the German Criminal Code to
complement Article 26(1) of the German Basic Law, outlined above. It
criminalises the preparation of a war of aggression in which the Federal
Republic of Germany is supposed to participate.67 Since the adoption of
the 3314 Definition a number of additional States have promulgated
relevant criminal laws. Article 316 of the 1974 Austrian Criminal Code
makes it an offence to undertake ‘from Austrian territory to change the
constitution of a foreign State or to divide off territory which is part of a
foreign State by force or threat with force’.68 Article 353 of the Criminal
Code of the Russian Federation of 199669 and Article 404 of the 1999
Criminal Code of Georgia70 make the planning, preparing, unleashing
or waging of an aggressive war a crime. Article 415 of the Republic of
Macedonia’s Criminal Code of 199671 and Article 130 of the 2004
Provisional Criminal Code of Kosovo72 establish the crime of calling
out or instigating aggressive war, while stirring up of an international
or a local armed conflict, propaganda of, and calls for, war among the
public, are crimes under the 2002 Criminal Code of Mongolia.73 Anyone
who ‘plans, prepares or wages aggressive war’ shall be punished under
Article 409 of the 1968 Penal Code of Bulgaria, as amended in 1998.74
Under Article 437 of the 2001 Criminal Code of the Ukraine:
1. Planning, preparation or waging of an aggressive war or armed conflict,
or conspiring for any such purposes, shall be punishable by
imprisonment for a term of seven to twelve years.
2. Conducting an aggressive war or aggressive military operations, shall
be punishable by imprisonment for a term of ten to fifteen years.75
Article 91 of the 2001 Estonian Penal Code makes ‘leading or partici-
pating in preparations for a war of aggression directed by one state
against another state or war violating international agreements or
security guarantees provided by the State’ and threatening to start a
war of aggression by a representative of the State, crimes, while Article
92 criminalises the incitement to war or other use of armed force in
violation of the generally recognised principles of international law.76
Under Article 150 of the 2003 Criminal Code of the Federation of Bosnia
and Herzegovina it is an offence to attempt to detach a part of the
territory of the Federation or to conjoin a part of its territory with
another entity by use of force or by threat of force.77
It is an offence under Article 139 of the 2002 Criminal Code of the
Republic of Moldova to plan, prepare, unleash or wage a war.78 Initiating,
conducting, making preparations to commit and publicly inciting to
initiate wars of aggression are offences under the 1997 Criminal Code
of the Republic of Poland.79 Article 384 of the 2003 Criminal Code of
the Republic of Armenia,80 Article 151 of the 1994 Criminal Code of
Uzbekistan,81 Article 395 of the 1998 Criminal Code of the Republic
of Tajikistan82 and Article 156 of the Criminal Code of the Republic of
Kazakhstan83 make planning, preparing, commencing or conducting an
aggressive war a crime. Propaganda and public exhortation to unleash an
aggressive war is also a crime under Article 157 of the 2004 Kazakhstan
Criminal Code. Calling for or instigating aggressive war, as well as orde-
ring and waging aggressive war are crimes under Article 442 of the 2003
Montenegro Criminal Code84 and Article 386 of the 2005 Criminal Code
of the Republic of Serbia.85
Attempting to recruit elements of the Portuguese Armed Forces for war
against a foreign state or territory endangering peaceful coexistence
between peoples is an offence under Article 237 of the 1982 Penal Code
of Portugal.86 Article 220 of the 1984 Argentina Criminal Code,87 Article
137 of the 1972 Criminal Code of Bolivia,88 Article 123 of the Ecuadorean
Penal Code of 197189 and Article 340 of the 1991 Penal Code of Peru90
make it an offence to violate treaties, truces, armistices or, in the case of
the Bolivian and Argentinian Codes, agreements of safe passage. Anyone
who violates a truce or armistice agreement between the Republic of
Chile and another enemy nation or among opposing forces at sea or land
can be punished under Article 113 of the Penal Code of Chile of 1874.91
Under Article 154 of the 2000 Penal Code of Venezuela recruiting
people or stockpiling weapons or preparing, forming or joining expedi-
tions or leaving the geographical area of Venezuela, in a hostile manner
to invade or attack a friendly nation or neutral, as well as building ships,
arming for war or increasing forces or equipment, its endowment or the
number of sailors to make war on a nation which is at peace with
Venezuela, are crimes. Penalties are higher if the hostile acts against a
friendly nation or neutral power have exposed the danger of war break-
ing out or harming friendly relations with the other nation, or war is
declared on Venezuela under Article 155.92 Article 312 of the 1982 Penal
Code of Panama provides that anyone who recruits, collects weapons or
performs other hostile acts not approved by the government and under-
taken within the territory of Panama or abroad against another State,
can be imprisoned for three to six years if as a result Panama is exposed
to the dangers of war or the breakdown of international relations and
ten years if the result is a declaration of war on Panama.93
Section 72 of the 1999 Criminal Code of Latvia provides that:
For a person who commits crimes against peace, that is, commits planning,
preparation or instigation of, or participation in, military aggression, or com-
mits conducting a war of aggression in violation of international agreements
binding upon the Republic of Latvia, or commits participation in a conspiracy
for the purpose of committing crimes mentioned in this section, the applicable
sentence is life imprisonment or deprivation of liberty for a term of not less than
three and not exceeding 20 years.94
Under Article 157 of the 1998 Criminal Code of the Republic of
(1) Whoever, regardless of whether a war has previously been declared
or not, wages a war of aggression by commanding an armed action of
one state against the sovereignty, territorial integrity or political
independence of another state, so that such an action is performed by
invasion or by an armed attack on its territory, aircraft or ships, or by
the blockading of ports or shores or by the military occupation of the
territory, or in some other way which denotes the forcible
establishment of rule over such a state, shall be punished by
imprisonment for not less than ten years or by long-term
(2) The same punishment as referred to in paragraph 1 of this Article shall
be inflicted on whoever, for the purpose of waging a war of aggression
of one state against another, commands or enables the sending of
armed mercenary groups or other paramilitary armed forces into a
state, so that these forces achieve the aims of a war of aggression.
(3) The same punishment as referred to in paragraph 1 of this Article shall
be inflicted on whoever acts according to a command for action from
armed forces or paramilitary armed forces for the purpose of waging a
war of aggression.
(4) Whoever call[s] [for] or instigates a war of aggression shall be punished
by imprisonment for one to ten years.95
Article 1 of Iraqi Law No. 7 of 17 August 1958 criminalises:
using the country’s armed forces against the brotherly Arab countries, threat-
ening to use such forces or instigating foreign powers to jeopardize its security
or plotting to overthrow the existing regime or interfere in their internal affairs
against its own interest, or spending money for plotting against them or giving
refuge to the plotters against them or attacking in international fields or
through publications their heads of state.
Finally, Article 14(3) of the Statute of the Iraqi Special Tribunal96 lists
as a crime:
The abuse of position and the pursuit of policies that may lead to the threat of
war or the use of force of the armed forces of Iraq against an Arab country, in
accordance with Article 1 of Law Number 7 of 1958, as amended.97
An examination of domestic legislation thus reveals that overall a
narrow definition of the State act element of the crime has been pre-
ferred. References to wars of aggression dominate. Not infrequent are
references to wars the key characteristic of which is that they are clearly
unprovoked. The US Armed Forces Field Manual and the Latvian Criminal
Code refer explicitly to crimes against peace. Annexation is the particular
preoccupation of the Austrian and Bosnian-Herzegovina criminal codes,
the former also contemplating regime change. The criminal codes of
Argentina, Bolivia, Chile, Ecuador and Peru focus on the violation of
treaties, truces or armistices – although this might be viewed as a refer-
ence to the long-lost second prong of the definition of wars of aggression
under the Charters of the IMT and IMTFE. The only real exception in
relation to domestic legislation is Iraq’s criminal provisions, which refer
to the mere threat of armed force (without any consequences having to
result) and interference in another State’s internal affairs.
Domestic laws relating to crimes against peace or the crime of aggres-
sion are not entirely theoretical. In 1999, the German Constitutional Court
rejected an application to open investigations relating to a complaint that
Germany’s involvement in NATO’s campaign against the Federal Republic
of Yugoslavia (FRY) gave rise to individual criminal responsibility under
section 80 of Germany’s Criminal Code. The Court ruled that irrespective
of the legality of the force used against FRY, aggressive war had to be
distinguished from a violation of the prohibition against the use of force
by the presence of a specific intent to disturb the peaceful coexistence of
peoples. It held that the NATO action could not be classified as a war of
aggression as it was a reaction to the Security Council’s determination
that a threat to international peace and security existed.98
In 2003, an attempt was made to have the German Federal Prosecutor
initiate prosecutions for crimes of aggression in relation to the
Coalition of the Willing’s invasion of Iraq, based on the German
Government’s granting to US armed forces the right of overflight and
allowing US bases in Germany to be used for activities related to military
operations, in addition to the deployment of German pilots on AWACS
aircraft conducting reconnaissance flights in Turkish airspace.99 The
attempt was rejected, the Federal Prosecutor determining that the
rights granted to the US did not amount to participation in a use of
force and the participation of German pilots in AWACS flights over
Turkey did not constitute preparation for the use of force against Iraq.
The Prosecutor thus left unanswered the question of whether or not the
use of force against Iraq amounted to a war of aggression within the
meaning of section 80 of the German Criminal Code.100 As Kress argues,
the Federal Prosecutor’s interpretation of participation within the
meaning of section 80 is limited to ‘the actual use of its armed forces,
or by way of a comparably massive military involvement’.101 Moreover,
perhaps unsurprisingly, the determination made in relation to the US’
use of German territory implies that the meaning of a ‘war of aggres-
sion’ under German law does not include the activities described in
Article 3(f) of the 3314 Definition.102
In 2005, the German Federal Administrative Court reviewed the court
martial of a German Major who refused to follow the order of a superior
to participate in the development of a software programme for a mili-
tary weapons system on the basis that the software could have been
used in combat in Iraq.103 In the course of its judgment the Court ruled
that the Coalition of the Willing’s invasion of Iraq was prima facie a
violation of Article 2(4). In relation to the German Government’s provi-
sion of assistance to the Coalition, the Court held that it had ‘grave
concerns’ as to the legality of such acts of support in terms of interna-
tional law. In the course of its judgment, the Court held that the legal
regime governing the aiding of a belligerent State by a non-party to a
conflict is derived from, inter alia, the 3314 Definition, as well as the
work of the ILC and international laws governing neutrality. The Court
specifically referred to Article 3(f) of the 3314 Definition and held that if
a State allows an armed attack to be carried out from its territory by
another State the actions can be attributed to the territorial State. As
Schultz notes, however, this statement was qualified by the Court’s
comment that the UN’s Member States did not claim that the 3314
Definition codified international law.104
The UK House of Lords’ decision in R v. Jones105 concerned damage
done by protestors to fuel tankers and bomb trailers and aggravated
trespass at two Royal Air Force bases in the weeks leading up to the
invasion of Iraq. The protestors’ defence relied on an argument that
they were using reasonable force to prevent the commission of a crime,
a defence under relevant domestic legislation. According to the Court,
the question for decision was whether the crime of aggression, if estab-
lished in customary international law, was a crime under the domestic
law of England and Wales. The House of Lords determined that it was
not required to rule whether the UK or the US had committed an act of
aggression, but instead whether, if they had done so, that would justify
the otherwise criminal conduct of the appellants.
Lord Bingham of Cornhill stated that it had not been suggested that
there was ‘any difference of substance’ between a crime against peace
and a crime of aggression and that as a matter of convenience he would
refer to the latter.106 He questioned the conclusions of the United States
Military Tribunal in the Ministries Case where it held that ‘aggressive
wars and invasions have, since time immemorial, been a violation of
international law, even though specific sanctions were not provided’.107
Lord Bingham continued: ‘[i]t may, I think be doubtful whether such
wars were recognised in customary international law as a crime when
the 20th century began. But whether that be so or not, it seems to me
clear that such a crime was recognised by the time the century
ended.’108 His Lordship recited a brief history of the crime109 then held:
the core elements of the crime of aggression have been understood, at least
since 1945, with sufficient clarity to permit the lawful trial (and, on conviction,
punishment) of those accused of this most serious crime. It is unhistorical to
suppose that the elements of the crime were clear in 1945 but have since
become in any way obscure.110
Lord Hoffman also held that ‘there is no doubt that this is a recognised
crime in international law’.111 His Lordship noted the then continuing
disagreements in relation to the crime’s enactment under the Rome
Statute but held that:
I think that upon analysis it will be found that these disputes are not about the
definition of the crime but about the circumstances in which the International
Criminal Court (as opposed to some domestic or ad hoc international tribunal,
such as the International Military Tribunal at Nuremberg) should try someone
for committing it. Of course the definition of a crime so recent and so rarely
punished will have uncertainties. But that is true of other crimes as well. If the
core elements of the crime are certain enough to have secured convictions at
Nuremberg, or to enable everyone to agree that it was committed by the Iraqi
invasion of Kuwait, then it is in my opinion sufficiently defined to be a crime,
whether in international or domestic law.112
This statement is of course less convincing because at the time there
was clearly disagreement among the States Parties to the Rome Statute
in relation to both jurisdictional and definitional issues. Moreover,
while Iraq’s invasion of Kuwait may well classify as a State act of
aggression, Lord Hoffman’s judgment confuses State responsibility
with individual criminal liability. Nonetheless, given the other Law
Lords agreed with the judgments of Lords Bingham and Hoffman,113
the House of Lords decision stands as a strong statement made by one of
the most respected domestic courts in the common law world confirm-
ing the existence of a customary international law crime of aggression.
While the House of Lords does not address the issue of the actual
definition of that crime, its frequent references to Nuremberg and
Tokyo jurisprudence indicate that the definition that is stated to be
sufficiently certain is at least grounded in that which was developed
by the IMT and IMTFE.114
While evidence of the customary law status of the crime was not
explicitly addressed, the ILC’s work on the Draft Code and the draft
Statute for an International Criminal Court demonstrates that the mem-
bers of the Commission shared a strong feeling that the international
community had accepted that the Nuremberg/Tokyo understanding of
crimes against peace had crystallised into customary international law.115
As widely remarked upon elsewhere, the proper means of establish-
ing customary international law is subject to some controversy and a
discussion of these issues is beyond the scope of this book. Regardless, it
is asserted that crimes against peace have become part of customary
international law. The reference to the 1945 incarnation of the crime is
deliberate. While there has been a shift in terminology since the adop-
tion of the UN Charter, there is a clear lack of State practice and opinio
juris to support a conclusion that all acts of aggression, or even a special
subset thereof, attract individual criminal responsibility under custom-
ary international law. In other words, the customary definition of the
State act element of the crime has not advanced past World War II
The first part of this contention is perhaps the more controversial but
there is sufficient evidence of State practice and opinio juris to establish
the customary nature of the crime, which will be referred to here, for
sake of convenience, as crimes against peace. While criticisms in rela-
tion to the invention of crimes against peace were certainly voiced
(primarily by academics) in the years immediately following the Allied
prosecution of their World War II enemies, the place of the crime in the
canons of international law was not rejected by States. On the contrary,
references to the crime were built into peace treaties and versions of it
are reflected in the domestic legislation of at least 35 States. The status
of the crime as one under international law was affirmed by the UN’s
Member States in Resolution 95(I); the same Members accepted with
approval the ILC’s Nuremberg Principles, which stated that crimes
against peace were punishable as a crime under international law.
They also included a reference to crimes against peace in the Refugee
Convention. Although their wording is not without uncertainty, Article
5(2) of the 3314 Definition, as well as Article 1(2) of the Friendly
Relations Declaration, point to a belief that wars of aggression give
rise to individual criminal responsibility. More importantly, records of
the debates between Member States in relation to these provisions
indicate that a belief was consistently espoused that wars of aggression
already attracted individual criminal responsibility under existing cus-
tomary law. The debate that produced such ambiguous texts related to
whether or not other acts of aggression also warranted criminal prose-
cution. Clearly, the members of the ILC never seriously questioned that
wars of aggression attracted individual criminal responsibility under
existing international law: again, the debate was the state of the law in
relation to other acts of aggression in the post-Charter era. The com-
ments of governments concerning the Draft Codes reveal that the view
of the ILC’s members in this regard was shared by Member States. The
House of Lords has expressed its opinion that the crime exists under
customary international law. And finally, as outlined in Chapter 1, an
overwhelming number of States indicated during the Rome Conference
that the crime was already part of international law, even if there was
continuing debate as to the appropriate definition of the modern incar-
nation of the State act element of the crime, a view that was later echoed
in the SWGCA. It might also be noted that a majority of commentators
agree with this view.116
As for the assertion that the customary crime is defined by reference
to wars of aggression, first of all, it is quite certain that neither the 3314
Definition, nor formulations based on language lifted from Article 2(4)
of the UN Charter, represent the customary definition of the State act
element of the crime. This is evidenced by the vociferous debates
between States sparked by the 1991 and 1996 Draft Code definitions
of the crime, and those held in the lead-up to, and during, the Rome
Conference, as well as in the years between Rome and Kampala. Rather,
it seems clear that the customary definition of the crime is pinned to its
World War II origins – a view shared by other commentators117 and
supported by the understanding of an act of aggression emerging under
the jus ad bellum outlined in Chapter 3.
The State practice and opinio juris referred to above on occasion make
reference to crimes against peace, which might be taken to refer to the
three-pronged definition that emerges from the constitutive instru-
ments of the post-war Tribunals. More commonly, however, reference
is made to wars of aggression. It is contended that the meaning of a
‘war of aggression’ under customary international law is identical to
that applied by the post-war Tribunals on the basis that all references
to wars of aggression are firmly anchored in Nuremberg and Tokyo
I specifically disagree with the assertion made by the English Court of
Appeal in the R v. Jones case (which was of course overturned on appeal
by the House of Lords) that the division among States in relation to
negotiations concerning the crime of aggression under the Rome
Statute signalled that there is no customary crime of aggression.118
The Court of Appeal’s judgment artificially conflates two separate
issues.119 The existence of a customary crime is not inconsistent with
a disagreement as to the mechanism of its prosecution. Moreover, it is
perfectly possible for there to exist a customary definition of a crime
that is considered to be outmoded or otherwise insufficient for future
purposes. A legislative process necessarily opens the door to a consid-
eration of whether pre-existing definitions are appropriate. Debate over
the shape the crime of aggression would take under the Rome Statute
does not of itself prove that there is no customary crime.
The US made an attempt in Kampala to win support for its view that the
definition being adopted did not represent customary international law.
It sought to add language to what ultimately became Understanding 4
that the amendments ‘shall not be interpreted as constituting a state-
ment of the definition of “crime of aggression” or “act of aggression”
under customary international law’.120 The fact that ‘it became clear
that there was not even a distant chance of States agreeing to this
proposal’121 should not be taken as saying something about State views
as to the current content of the customary crime. It more likely repre-
sents some level of discomfort associated with the swathe of proposals
advanced by the US at the eleventh hour, and the view that although
it might not have represented customary law before the Review
Conference in Kampala, the definition may well play a role in helping
to crystallise a broader definition under customary law in years to come.
In summary, it is plain that the State act element of the crime under
Article 8bis goes well beyond the content of that element of the crime
under customary international law.122 As outlined in Chapter 3, Articles
1 and 3 of the 3314 Definition, which are replicated in Article 8bis (2),
capture an extremely broad range of conduct. The effect of the addi-
tional threshold in draft Article 8bis (1) is not entirely clear; nevertheless
it seems highly unlikely that in requiring a certain level of seriousness
and evident illegality it sets the bar as high as importing a de facto
requirement that a ‘war’ has taken place. The intention of the majority
of the SWGCA was certainly for a much broader range of acts to be
captured by the definition.123 Obviously, the definition also lacks any
requirement of animus aggressionis mirroring the objects towards which
wars must be directed under customary international law. As such, it
can be concluded that Article 8bis criminalises a significantly broader
range of conduct than the customary definition of the State act element
of the crime.
What is the consequence of this inconsistency? As noted in the intro-
duction to this section, where the Court exercises its jurisdiction
pursuant to a Security Council referral or an ad hoc acceptance of the
Court’s jurisdiction under Article 12(3) over crimes committed on the
territory, and by the nationals, of non-States Parties it cannot rely on
the prior consent of the relevant States to be bound by the Rome Statute.
The only basis on which the Court can exercise such retrospective
jurisdiction without violating the nullum crimen sine lege principle
enshrined under Article 22(1) of the Statute124 (in addition to Article
15(1) of the International Covenant for Civil and Political Rights125 and
potentially also Article 34 of the Vienna Convention on the Law of
Treaties)126 is where the conduct concerned amounted to a crime
under customary international law (absent a corresponding domestic
prohibition). Thus in the case of Security Council referrals involving a
crime of aggression committed by a national of a non-State Party on the
territory of a non-State Party (Article 12(3) appears not to apply to the
crime of aggression, see further below)127 an accused will have a strong
argument that he or she cannot be held criminally responsible for any
conduct falling under the definition of Article 8bis (2) that does not
amount to a war of aggression.128

Making the ICC an arbiter of the grey areas in the jus ad bellum

It is stating the obvious to say that there exist areas of genuine dispute
in relation to the scope of the prohibition of the threat or use of
force. These so-called ‘grey areas’ are well documented. They include
intervention in a civil war on request (including in the more specific
instance of a war of national liberation),129 unilateral humanitarian
intervention,130 force exercised in the course of the protection or rescue
of nationals abroad,131 reprisals,132 and, more generally, force that is
not directed against the territorial integrity or political independence of
a State that is otherwise consistent with the Purposes of the United
Nations.133 Also contested is the scope of the right of self-defence. This
issue has been well ventilated by international lawyers and is hotly
contested by States. Key points of debate are whether or not Article 51
of the UN Charter authorises the use of inter-State armed violence in
anticipation of an imminent armed attack, or whether permission to
use force in such circumstances under customary international law
survived the introduction of Article 51 (anticipatory self-defence). Far
more controversial is whether self-defence can be exercised preven-
tively to guard against a possible future attack (pre-emptive self-
The existence of the grey areas stems from immutable factors: the
limits of language; the failure of the collective security system envis-
aged by the Charter; a growing consciousness that gross violations of
international humanitarian and human rights law must not be toler-
ated; and the changing dynamics of the international community. In
addition to these systemic causes is the endurance of the primacy of
national interests – national interests that have a stake in maintaining
as much leeway as possible in relation to the prohibition of the use of
force. Debates in relation to the grey areas are nuanced: often argument
centres on the literal content of the law, other times, however, the focus
is on whether or not there are certain circumstances (such as the
objective with, and contingency for, which force is used) that justify
or pardon an act that is technically unlawful (and which, for a variety of
reasons, a majority of States wish it so to remain).135
It is not the role of this book to contribute to the legal debate
surrounding the grey areas. Indeed my argument is that it is not the
role of international criminal law to find answers to these issues. As Fife
and Kress have written, the jus ad bellum should not be developed
through the back door of international criminal law.136
In this context Bassiouni has explained that ‘international crimes
have developed to date, without . . . an agreed-upon definition of what
constitutes an international crime, what are the criteria for international
criminalization, and how international crimes are distinguished’.137
Both the harm principle and legal moralism (popular philosophies
of criminalisation in the context of domestic law) certainly seem insuffi-
cient to explain the international criminalisation process. This is
principally because they ignore what can be identified as the key feature
of international criminalisation: the governance of normative develop-
ment by inter-State consensus. In other words, international criminal law
is generally a reflection of the prohibitions that attract the broad support
of the international community. Such consensus, above and beyond
notions of moral wrongfulness and harm caused to the fundamental
interests of the international community, is what ordinarily must be
present in order for conduct to become a crime under international
In the case of the crime of aggression, the jus ad bellum is the founda-
tion upon which the criminal law rests.139 At the current stage of
international relations it is patently impossible to attain consensus in
relation to the grey areas outlined above. Some would go further and
argue that in order to preserve the integrity of the core of the prohib-
ition of the threat or use of force in a system where collective security
works only in an ad hoc and imperfect manner, it is necessary that there
be a degree of flexibility of interpretation, that allows States to tolerate
‘deviances’, while at the same time affirming the existence of the
The problem of grey areas was widely recognised by the SWGCA and
the ASP. In response it was decided that activities of questionable legal
status should not attract individual criminal responsibility. Rather,
however, than carving out explicit exceptions for such actions, or devel-
oping a narrow definition that was restricted to conduct that was
uncontrovertibly unlawful, thereby stepping around acts of contested
legal status, States adopted a definition that defers the problem to the
ICC. In other words, as argued above, by requiring proof of a ‘manifest
violation’ of the Charter the ASP has attempted to restrict the content of
the crime of aggression to conduct that is prohibited by an inter-State
consensus. The result, however, is that the burden of determining
where that consensus lies has been shifted to the ICC.
Kress has argued that ‘reasonable international lawyers will find it
comparatively easy to identify those instances of the use of force that
fall within the grey areas. If one studies the more recent treatises of the
subject, one will almost invariably find the same list of controversial
cases.’141 Indeed, such a list was produced above. This argument, how-
ever, ignores the complexities of the issue. Outside of Iraq’s invasion of
Kuwait it is difficult to think of a use of force in the post-Charter era that
has not had legal arguments advanced in justification and opprobation –
however unconvincing some of those arguments might be. Eminent
international jurists and States vehemently disagree about the current
state of the law, expressing strong views that each of the activities
described as a grey area by this book are in fact unambiguous violations
of the Charter or clearly lawful. Thus, there is a chance that the protec-
tion afforded by the manifest violation threshold will be insufficient,
depending on the view of international law adopted by the judges of the
Court, who could well dismiss contrary views as misguided or ill-
Alternatively, Paulus could be right in describing the manifest viola-
tion threshold as an extremely restrictive standard; ‘[w]hat, after all’, he
says, ‘is obvious for one is completely obscure to the other, in particular
in international law’.142 In other words, overly cautious judges of the
ICC, in the face of any contrary arguments about the illegality of a use of
force, may feel they have no choice but to determine that the threshold
has not been met. It is easy to be dismissive of such concerns, but as
Kress himself wrote in the course of the crime of aggression negotia-
tions, international criminal law is ‘ill-equipped to decide major con-
troversies about the content of existing legal rules’.143
Consider, for example, the issue most likely to be contested by a
defendant in any given case: self-defence. The definition of the crime
of aggression under Article 8bis leaves the scope of self-defence to be
determined by the ICC on a case-by-case basis. There is some merit in
this approach: although they are not exhaustive, international law’s
rules on self-defence are arguably sufficiently certain to be interpreted
and applied by the ICC. It is, however, crucial that States have a clear
understanding of the scope of conduct excluded from the definition of
the State act element of the crime by virtue of self-defence before any
trial is commenced.144 The existing ambiguity is understandably likely
to leave States feeling uneasy that the ICC will not share their
interpretation of the principal exception to the prohibition of the use of
force. While the need for the Court to engage in a degree of judicial
interpretation is inevitable, leaving such sensitive, highly contested and
complex issues to be determined by the ICC is something of a gamble for
international criminal law.
Moreover, as noted above, some of the disagreement surrounding the
prohibition is not about the literal content of the law, but as to whether
breaches of the law should be tolerated in certain circumstances.
Arguably, unauthorised humanitarian intervention falls into this
My reading of interventions in debates and corridor discussions over
the years of the SWGCA’s negotiations suggests that more than any
other action, unauthorised humanitarian intervention was what
States Parties had in mind in supporting the evident illegality require-
ment. Ultimately, however, it is unclear whether the threshold serves
this purpose. As Barriga writes: ‘[s]ome . . . regard the threshold clause as
the entrance door for the legalisation of humanitarian interventions
without Security Council authorisation, whereas others regret that it
is not’.145
As noted above, in Kampala the US sought to insert an understanding
that would have explicitly excepted unilateral humanitarian interven-
tions. That understanding was soundly rejected by States Parties in the
course of bilateral negotiations. Kress, a member of the German
Delegation, which was one of the most vocal proponents of the evident
illegality interpretation of the manifest violation threshold, says of this:
Importantly, the fact that the exclusion of certain instances of the use of force by
a state was not discussed further does not mean that there was necessarily
disagreement with the United States on substance. It is worth specifically under-
lining this point with respect to the single most sensitive American proposal,
which purported to explicitly exclude genuine forcible humanitarian interven-
tions from the scope of draft Art 8 bis. The main concern here was that it would
not be appropriate to address key issues of current international security law in
the form of understandings drafted not with all due care, but in the haste of the
final hours of diplomatic negotiations.146
Certainly I think it true that States were of the view that there was a
limit to what could be done at the eleventh hour (and arguably what
should be done in the sense of accommodating the US – lessons had
been learned from Rome, where numerous provisions were watered
down in an attempt to win the US over, only to be met with the reward
of the US calling for a vote as the Conference drew to a close). It is also
important to underline that States did not necessarily agree with the US
on the substantive question of the exclusion of humanitarian interven-
tion. A very significant number of States remain opposed to unilateral
humanitarian intervention on the basis that it violates sovereignty and
that it masquerades as a form of neo-colonialism. I also think a very
clear majority of international lawyers would advise that while a rule of
customary international law making an exception for humanitarian
intervention might be in the process of crystallising, there is as yet no
rule that permits unauthorised humanitarian intervention under inter-
national law. As indicated above, the better view, I think, is that unau-
thorised humanitarian interventions are sometimes tolerated by the
international community on the basis that they are viewed as legiti-
mate – not legal.
This begs the question of whether ‘legitimate but unlawful’ uses of
force are excluded from the definition of a crime of aggression by
Understanding 6 relating to the meaning of an ‘act of aggression’, or
the manifest violation threshold. This will ultimately depend how the
́paratoires are read. Literally they refer to ‘legal’ grey areas, but
travaux pre
it seems the clear intent of States was to exclude humanitarian inter-
ventions – a fact attested to in the writings of others who participated in
the negotiations.
Ultimately, the reader may not share my characterisation of unau-
thorised humanitarian interventions as illegal. This is not fatal to my
argument. What is undeniable is that the determination of the status of
such actions has been left to the judges of the ICC.
Of course, the foregoing has been premised on an assumption that we
are talking about genuine humanitarian interventions, aimed solely at
protecting vulnerable civilians within a sovereign State from mass
atrocity crimes. What happens when ulterior motives are added to the
mix? Will a use of force aimed at protecting civilians being subjected to
mass atrocity crimes but also towards installing a governing power
more sympathetic to the intervening States, thereby securing better
access to, say, oil, meet the threshold test? This, not unlikely, scenario
perhaps more sharply illustrates the difficult decisions that will be
faced by the ICC.
The reader might argue that any Prosecutor with an ounce of political
awareness will avoid such situations and focus attention on uses of
force that more closely resemble Iraq’s invasion and attempted annex-
ation of Kuwait. But this could be the thin edge of a very significant
wedge. The first Prosecutor of the ICC, Louis Moreno-Ocampo, repeat-
edly said that his job was to follow the evidence, not to engage in
political debates – and there are cogent reasons (principally the integ-
rity of justice) for wanting the Prosecutor to make his or her decisions
absent political considerations. One might argue that Article 16 can be
exercised to prevent the Court having to touch difficult political issues.
Article 16, however, requires an affirmative vote, or abstention, from a
majority of the members of the Security Council, including all of the P5,
something that could be difficult to secure in the current geopolitical
The result is that the ICC could well be engaged in making difficult
decisions regarding the content of the jus ad bellum – which, I would
argue, is not how international criminal law should work. Apart from
anything else, it entails a significant risk that the Court’s reputation will
be tarnished, as it seems highly likely that (legitimately or not) the mere
making of such decisions (correct or not) will provide States with
ammunition to criticise the ICC.147 Alternatively, in the face of compet-
ing legal arguments mounted from the sidelines, the Prosecutor may be
forced to make a pre-emptive decision that in light of such disagree-
ments such uses of force cannot satisfy the manifest violation thresh-
old. This could in effect almost turn the crime into a dead letter law.
Either scenario would be a deeply disappointing consequence of finally
having agreed the definition of the crime of aggression.

Article 31: grounds for excluding criminal responsibility

Article 31(1) of the Rome Statute provides a non-exhaustive list of
grounds on which a person will not be held criminally responsible,
including that the accused suffered from a mental disease or defect,
or was in a state of intoxication that destroyed his or her ability to
control his or her conduct; he or she was suffering from duress; or
was acting reasonably to defend himself or herself or another person
against an imminent and unlawful use of force in a manner propor-
tionate to the degree of danger. Article 31(3) is a catch-all provision,
which provides that the Court may consider additional grounds for
excluding criminal responsibility derived from the law applicable to
the ICC under Article 21.
Clark has asserted that Article 31(3):
is likely to be particularly significant where a leader alleges that in fact the state
was acting in self-defence, with the approval of the Security Council, or pur-
suant to any other ground which he or she alleges has the support of treaty or
customary law. It is, for example, here that arguments about the legality of
humanitarian law need to be structured.148
This is incorrect. Put simply, it would never be necessary for an
accused to rely on any jus ad bellum grounds supposedly excusing crim-
inal responsibility for the crime of aggression arising from ‘applicable
treaties and the principles and rules of international law’149 (even if it is
conceded that this would be possible). If a defendant successfully argued
that an inter-State use of armed force was an exercise of self-defence,
this would prevent the Prosecutor from being able to establish the third
element of the crime. As such, there would be no need to resort to
grounds on which criminal responsibility could be excused. The situa-
tion in relation to unlawful uses of force that fail to meet the manifest
threshold is exactly the same. Rather than casting humanitarian inter-
vention as a ground for excusing criminal responsibility it should prop-
erly be seen as an argument that would be submitted by the defence
aimed at preventing the prosecution from establishing, beyond a rea-
sonable doubt, the fifth element of the crime.
As such, the better view is that Article 31 applies to the crime of
aggression in precisely the same manner as it does to the other Statute
crimes, with no special considerations applying.


This chapter has explored the meaning of the ‘manifest violation’
threshold and the factors character, gravity and scale, which are to be
used to gauge whether that threshold has been met. It has been estab-
lished that Article 31 has no special role to play in relation to the crime
of aggression. A number of criticisms associated with the definition of
the State act element of the crime of aggression have also been
addressed. It has been demonstrated that the definition of the State
act element of the crime is not in danger of violating the nullum crimen
sine lege principle (at least when applied to States Parties). It has further
been shown that the ASP has correctly restricted the conduct captured
by the definition in a manner consistent with the scheme of the Rome
Statute, and that this will have no effect on the lawfulness of State uses
of force that have not been criminalised, even if it cannot be said
whether the dividing line will be set too high or too low by the Court
in future decisions.
On the other hand it has been established that the inconsistency of
the definition under the Rome Statute with the customary definition of
the crime opens the door to challenges to the Court’s jurisdiction where
situations involving the territory and nationals of non-States Parties are
referred to the Court by the Security Council – at least when they
involve conduct that falls outside the customary definition of the
crime. Finally, it has been shown that the Court has been left to deter-
mine where areas of consensus in relation to the jus ad bellum lie, and
that in the course of making its decisions the Court will have to deter-
mine highly sensitive aspects of public international law.
Since the adoption of the definition of the crime of aggression in
Kampala, Kress and von Holtzendorf have acknowledged that some
aspects of the definition remain problematic but have expressed the
view that any attempt to eliminate such problems ‘would come very
close to simply giving up on the project of defining the crime’.150 I do
not share this view. I believe it is perfectly possible to construct a
definition that avoids all of the problems that I have identified with
the definition adopted under Article 8bis of the Statute. In an acknowl-
edgement that this particular ship has now sailed, and that there was
little appetite for the construction of a novel definition (States prefer-
ring to cling to inadequate but agreed language), I do not include such a
definition in this book, but I hope to publish it elsewhere for the
academically curious to consider.
Unlike some commentators, my concerns regarding the definition do
not lead me to call for States to refuse to ratify the amendments, or to
avoid activating the Court’s jurisdiction in 2017. In essence, I believe
that the crime of aggression is too important for that. I also do not see
the concerns as fatal, it being naive to consider the Rome Statute an
otherwise perfect instrument. I also happen to think that some of the
most important consequences of the criminalisation of acts of aggres-
sion will be the chilling effect it has in preventing the unlawful use of
force in the first place.151 What I would urge is that States Parties think
carefully about these problems in the context of making decisions about
issues such as the election of judges, and in considering whether further
amendments to the Statute are possible. The Security Council will need
to be mindful of potential problems arising from the inconsistency of the
definition, at least at this point in time, with customary international
law. And the Court and the OTP will, in my view, need to engage in a
careful information campaign in order to manage expectations.


1 Andreas Paulus, ‘Second Thoughts on the Crime of Aggression’ (2009) 20(4) European
Journal of International Law 1117, 1121; Solera, ‘Lessons Not Learned’, 808–811; Heinsch,
‘The Crime of Aggression After Kampala’, 726–728; Marko Milanovic, ‘Aggression and
Legality: Custom in Kampala’ (2012) 10 Journal of International Criminal Justice 165, 170;
Mary Ellen O’Connell and Mirakmal Niyazmatov, ‘What is Aggression? Comparing the
Jus ad Bellum and the ICC Statute’ (2012) 10 Journal of International Criminal Justice 189,
201–204; Akande, ‘Prosecuting Aggression’, 5.
2 Statement by Harold Hongju Koh, Legal Adviser, US Department of State, Review Conference of the
International Criminal Court, Kampala, Uganda, 4 June 2010, on file with author.
3 Notes of the June 2006, June 2007, December 2007 and June 2008 SWGCA Meetings, on
file with author.
4 Proposal Submitted by Egypt and Italy on the Definition of Aggression, UN Doc. A/AC.249/1999/
WG.1/DP.6 (1997); Draft Statute for an International Criminal Court, 13–14; Proposal Submitted
by Guatemala on Document PCNICC/2001/WGCA/DP.2, UN Doc. PCNICC/2001/WGCA/DP.3
(2001); 2002 Discussion Paper Proposed by the Coordinator; Suggestion Regarding Paragraph 1 of
the 2007 Chairman’s Paper, circulated informally to the SWGCA by France, June 2007, on
file with author.
5 Proposal by Germany, Article 20: The Crime of Aggression, An Informal Discussion Paper, UN Doc.
A/AC.249/1997/WG.1/DP.20 (1997); Proposal Submitted by Germany: Definition of the Crime of
Aggression, UN Doc. PCNICC/1999/DP.13 (1999); Proposal Submitted by Germany, The Crime
of Aggression: A Further Informal Discussion Paper, UN Doc. PCNICC/2000/WGCA/DP.4 (2000);
Definition of Aggression in the Context of the Statute of the International Criminal Court, ICC Doc.
ICC-ASP/4/SWGCA/1 (2005); Response to Discussion Paper Three, Compiled by Phani Livada,
circulated informally to the SWGCA, June 2006, on file with author, responses by
Germany, Greece and Spain to Question 3.
6 June 2006 SWGCA Report, [19]; January 2007 SWGCA Report, [16].
7 June 2007 SWGCA Report, [55]–[57]; December 2007 SWGCA Report, [25]–[26].
8 June 2008 SWGCA Report, [24]. The amendment was introduced at the initative of the
author in an attempt to reverse the trend of SWGCA Reports not capturing the ‘legal
grey areas’ function of the proposed threshold.
9 June 2008 SWGCA Report, [24]. In its February 2009 Report, the SWGCA reverted to a
reference to the exclusion of ‘borderline cases’: February 2009 SWGCA Report, [13].
10 Barriga, ‘Negotiating the Amendments’, 29; Kress, ‘Time for Decision’, 1138;
James Potter, ‘The Threshold in the Proposed Definition of the Crime of Aggression’
(2008) 6 New Zealand Yearbook of International Law 155, 165.
11 Heinsch, ‘The Crime of Aggression After Kampala’, 727.
12 Paulus has expressed the view that ‘“Character”, of course, is so indeterminate that it is
also meaningless’. Paulus, ‘Second Thoughts’, 1121.
13 Van Schaack, ‘Humanitarian Intervention’, 486.
14 1999 Proposal Submitted by Germany; 2000 Proposal Submitted by Germany.
15 Kress & von Holtzendorf, ‘The Kampala Compromise’, 1193; Potter, ‘The Threshold in
the Proposed Definition’, 165.
16 Heinsch, ‘The Crime of Aggression After Kampala’, 729.
17 Solera, ‘Lessons Not Learned’, 808–809 raises similar concerns.
18 Non-Paper on possible further understandings (Annex III of the Conference Room Paper),
informally circulated by Germany on 8 June 2010, on file with author.
19 Kress & von Holtzendorff, ‘The Kampala Compromise’, 1206.
20 Kress et al, ‘Negotiating the Understandings’, 96.
21 Kress & von Holtzendorff, ‘The Kampala Compromise’, 1207.
22 Susan Lamb, ‘Nullum Crimen, Nulla Poena Sine Lege in International Criminal Law’ in
Cassese, Gaeta & Jones, The Rome Statute, 733, 752–753.
23 Cassese, International Criminal Law, 49; Lamb, ‘Nullum Crimen’, 753; Bruce Broomhall,
‘Article 22’ in Triffterer, Commentary on the Rome Statute, 713, 725.
24 Ibid.
25 February 2009 SWGCA Report, [13]. See also June 2008 SWGCA Report, [70].
26 Daniel D. Ntanda Nsereko, ‘Aggression under the Rome Statute of the International
Criminal Court’ (2002) 71 Nordic Journal of International Law 497, 503. See also Weisbord,
Prosecuting Aggression’, 220 and Paulus, ‘Second Thoughts’, 1122, who argue that
limiting the crime of aggression to ‘manifest violations’ may give a carte blanche to all
incidents of aggression that are not manifest.
27 Nsereko, ‘Bringing Aggressors to Justice’, 24.
28 Ibid.
29 In relation to war crimes see Michael Bothe, ‘War Crimes’ in Cassese, Gaeta & Jones, The
Rome Statute, 379, 387.
30 Paulus, ‘Second Thoughts’, 1124.
31 Draft Paper on Criteria for Selection of Situations and Cases, unpublished paper by the OTP,
June 2006.
32 Emphasis added. See paragraphs 4 and 9 of the Preamble to the Rome Statute and
Elements of Crimes, ICC Doc. ICC-ASP/1/3 (2002), Part II(B), 116 in relation to crimes
against humanity.
33 See United Nations Diplomatic Conference of Plenipotentiaries on the Establishment of
an International Criminal Court, Summary Record, 5th Plenary Meeting, UN Doc. A/
CONF.183/SR.5 (1998), statement by Lebanon, 7 (emphasis added). For statements of
similar effect see Summary Record, 2nd Plenary Meeting, UN Doc. A/CONF.183/SR.2 (1998)
interventions by Trinidad and Tobago (4), Japan (6), Sweden (8), Canada (8); Summary
Record, 3rd Plenary Meeting, UN Doc. A/CONF.183/SR.3 (1998): Holy See (2–3), Czech
Republic (4), United Republic of Tanzania (5), Latvia (6), Brazil (7), Pakistan (12);
Summary Record, 4th Plenary Meeting, UN Doc. A/CONF.183/SR.4 (1998): Philippines (3),
Colombia (5), Ukraine (7), Austria (8), Former Yugoslav Republic of Macedonia (8),
Afghanistan (11); Summary Record 5th Plenary Meeting, UN Doc. A/CONF.183/SR.5 (1998):
Brunei Darussalam (3), Tajikistan (4), Guinea (4), Hungary (4), Zambia (5), Azerbaijan (5),
Poland (6), Bulgaria (8), USA (8); Summary Record 6th Plenary Meeting, UN Doc. ICC/
CONF.83/SR.6 (1998): Belgium (2), Ireland (3), Paraguay (10); Summary Record 7th Plenary
Meeting, UN Doc. A/CONF.183/SR.7 (1998): Malaysia (7), Samoa (8), Vietnam (10) and
Nigeria (11).
34 December 2007 SWGCA Report, [23].
35 Hermann Von Hebel & Darryl Robinson, ‘Crimes Within the Jurisdiction of the Court’ in
Lee, The International Criminal Court 79, 122; Leena Grover, ‘A Call to Arms: Fundamental
Dilemmas Confronting the Interpretation of Crimes’ (2010) 21(3) European Journal of
International Law 543, 567; Gennady M. Danilenko, ‘The Statute of the International
Criminal Court and Third States’ (2000) 21 Michigan Journal of International Law 445, 481.
Kress & von Holtzendorf, ‘The Kampala Compromise’, 1188 argue that it was agreed
this approach would be extended to the crime of aggression.
36 Statement by Israel, United Nations Diplomatic Conference of Plenipotentiaries on the
Establishment of an International Criminal Court, Official Records, Vol. II, Summary
Records of the Plenary Meetings and of the Meetings of the Committee of the Whole, UN Doc. A/
CONF.183/13(vol. II) (1998), 167. Statements to similar effect were made by Japan (67);
China (124 and 299); USA (159 and 280); Germany (159); Spain (161); Thailand (163);
Egypt (164 and 335); India (168); Italy (194); and the Dominican Republic (285).
37 Ibid., statements by the UK (150); Slovenia (151); Canada (154–155); Israel (155); Syrian
Arab Republic (158); New Zealand (160); Greece (160); Belgium (162); France (164);
Jordan (187); China (270); Switzerland (277); Brazil (277); Republic of Korea (278); Bosnia
and Herzegovina (285); Indonesia (287); and Russia (289). It is, of course, recognised that
agreement as to the need for the crimes under the Court’s jurisdiction to be defined in a
manner that is consistent with customary international law is distinct from an
agreement as to the content of that law, a subject over which there were numerous
debates in Rome.
38 Von Hebel & Robinson, ‘Crimes within the Jurisdiction’, 89, 104, 123; William
A. Schabas, An Introduction to the International Criminal Court, Cambridge University Press,
2001, 23. For a comparison of the Rome Statute’s definitions of crimes with customary
international law see Antonio Cassese, ‘Genocide’ in Cassese, Gaeta & Jones, The Rome
Statute, 335; Antonio Cassese, ‘Crimes Against Humanity’ in ibid., 353; and Bothe, ‘War
Crimes’, 379.
39 Meron, ‘Defining Aggression’, 8.
40 Broomhall, ‘Article 22’, 713, 720. See also Grover, ‘A Call to Arms’, 567–568; Danilenko,
‘Third States’, 468.
41 During the negotiations on the crime of aggression, several commentators
recommended that the crime of aggression be based on customary international law.
See for example Muller-Schieke, ‘Defining the Crime of Aggression’, 415; Claus Kress,
‘The Crime of Aggression Before the First Review Conference of the ICC Statute’ (2007)
20 Leiden Journal of International Law 851, 858–859, 864; Sean D. Murphy, ‘US View of
Crime of Aggression’ (2001) 95(2) American Journal of International Law 400, 400–401.
42 McDougall, ‘Time to Catch Up or Part Ways’, 131–167.
43 Signed 10 February 1947, 49 UNTS 3 (entered into force 15 September 1947),
Article 45(a).
44 Signed 10 February 1947, 42 UNTS 33 (entered into force 15 September 1947),
Article 6(a).
45 Signed 10 February 1947, 41 UNTS 49 (entered into force 15 September 1947),
Article 5(a).
46 Signed 10 February 1947, 48 UNTS 228 (entered into force 15 September 1947), Article 6(a).
47 Signed 10 February 1947, 41 UNTS 167 (entered into force 15 September 1947), Article 6(a).
48 Opened for signature 8 July 1951, 189 UNTS 150 (entered into force 22 April 1954),
Article 1(f).
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53 Ibid., Vol. XV, 32.
54 Ibid., Vol. III, Annex III, 83–84.
55 Ibid., Vol. III, Annex III, 105–106.
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57 Ibid. and Resolution on the Formulation of the Principles Recognised in the Charter of the Nurnberg
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61 Johnson, ‘The Draft Code of Offences’, 446; Parry, ‘Some Considerations Upon the
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62 C. A. Pompe, Aggressive War: An International Crime, The Hague: Martinus Nijhoff,
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63 Ibid.
64 Brownlie, International Law, 190 agrees with this conclusion.
65 Section 498, United States Department of the Army, Field Manual No. 27–10, The Law of
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96 Coalition Provisional Authority, The Statute of the Iraqi Special Tribunal (2004) 43
International Legal Materials 231.
97 An excellent analysis of domestic legislation related to the crime of aggression can be
found in Astrid Reisinger Coracini, ‘Evaluating Domestic Legislation on the Customary Crime
of Aggression under the Rome Statute’s Complementarity Regime’ in Carsten Stahn &
Goran Sluiter (eds.), The Emerging Practice of the International Criminal Court, Leiden:
Martinus Nijhoff Publishers, 2009, 725.
98 Paulus, ‘Peace Through Justice’, 27; Claus Kress, ‘The German Chief Federal
Prosecutor’s Decision Not to Investigate the Alleged Crime of Preparing Aggression
Against Iraq’ (2004) 2 Journal of International Criminal Justice 245, 256.
99 Paulus, ‘Peace Through Justice’, 28–30; Kress, ‘The German Chief Federal Prosecutor’,
100 Ibid.
101 Ibid., 248.
102 Ibid., 249.
103 Nikolaus Schultz, ‘Case Note – Was the War on Iraq Illegal? The Judgment of the
German Federal Administrative Court of 21st June 2005’ (2006) 7 German Law Journal,
electronic resource.
104 Ibid., 1, 2, 5–7. In relation to failed attempts to initiate prosecutions under s.80 of
Germany’s Criminal Code, see Sascha Mueller, ‘The Crime of Aggression under
German Law’ 6 (2008) New Zealand Yearbook of International Law 183, 191–193.
105 [2006] UKHL 16. Cf. the earlier decisions in the case [2004] EWCA Crim 1981 and [2005]
EWHC 684 (Admin).
106 [2006] UKHL [4].
107 Ibid., [12].
108 Ibid.
109 Ibid., [13]–[18].
110 Ibid., [19].
111 Ibid., [44].
112 Ibid., [59].
113 Ibid., [96]–[98]. Lord Mance added: ‘I agree in particular that there is under public
international law a crime of aggression which is, as history confirms, sufficiently
certain to be capable of being prosecuted in international tribunals’ [99].
114 The House of Lords held that a crime in international law does not automatically
become assimilated into domestic English law (Bingham, [23]). Given there had been
no parliamentary enactment of the crime and English courts cannot establish new
crimes ([28]), the House of Lords concluded that the crime of aggression was not a
crime under the domestic law of England and Wales within the meaning of the
relevant legislation ([31]).
115 See for example Report of the 46th Session of the ILC, 38.
116 See for example Cryer et al, An Introduction to International Criminal Law, 262, 263;
Schachter, ‘The Right of States to Use Armed Force’, 114; Dinstein, War, Aggression and
Self-Defence, 113; M. Cherif Bassiouni, ‘International Law and the Holocaust’ (1979) 2
Californian Western International Law Journal 201, 235; Meron, ‘Defining Aggression’, 6;
Nigel D. White, Keeping the Peace: The United Nations and the Maintenance of International
Peace and Security, Manchester University Press, 1993, 53; Robert Cryer, ‘Aggression at
the Court of Appeal’ (2005) 10(2) Journal of Conflict and Security Law 209, 225, 226, 229;
Reisinger Coracini, ‘Evaluating Domestic Legislation’, 725; C. P. DeNicola, ‘A Shield for
the “Knights of Humanity”: The ICC Should Adopt a Humanitarian Necessity Defense
to the Crime of Aggression’ (2008–2009) 30 University of Pennsylvania Journal of
International Law 641, 652; Mark A. Drumbl, ‘The Push to Criminalise Aggression:
Something Lost Amid the Gains?’ (2009) 41 Case Western Reserve Journal of International
Law 291, 291–292; Gerhard Kemp, Individual Criminal Responsibility for the International
Crime of Aggression, Antwerp: Intersentia, 2010, 85, 144; Edoardo Greppi, ‘State
Responsibility for Acts of Aggression Under the United Nations Charter: A Review of Cases’ in
Roberto Bellelli (ed.), International Criminal Law: Law and Practice from the Rome Statute to Its
Review, Farnham: Ashgate, 2010, 499, 501; Ambos, ‘The Crime of Aggression After
Kampala’, 478.
117 See for example Cassese, ‘On Some Problematical Aspects of the Crime of Aggression’,
845; Drumbl, ‘The Push to Criminalise Aggression’, 305; Paulus, ‘Second Thoughts on
the Crime of Aggression’, 1118; A. Zimmermann, ‘Article 5’ in Otto Triffterer, Commentary
on the Rome Statute of the International Criminal Court: Observers’ Notes, Article by Article (2nd
ed.) Munich: C. H. Beck, 2008, 136; Cryer et al, An Introduction to International Criminal
Law, 273. Cf. the suggestion made by Milanovic, ‘Aggression and Legality’, 183 that the
manifest threshold may restrict the definition to its customary content. Milanovic’s
argument is based on the threshold’s exclusion of the grey areas surrounding the
prohibition. He offers, however, no argumentation to support his assertion and
Milanovic himself appears to consider crimes against peace the better representation
of the customary crime (184).
118 Jones & Milling, Olditch & Pritchard & Richards v. Gloucestershire CPS [2004] EWCA Crim 1981,
[43]. The Court of Appeal referred to the SWGCA’s division over the jurisdictional
question and stated in this context that there could be no ‘firmly established rule of
international law which establishes a crime of aggression . . . where there is no
consensus as to an essential element of the crime’. The same, perhaps more cogent,
argument could be made in relation to the definitional question.
119 Cryer (‘Aggression at the Court of Appeal’, 228) discusses the fact that the Court of
Appeal’s judgment conflated the jurisdictional and definitional issues. The Court of
Appeal in addition conflated the issues of a debate over the shape of provisions relating
to the crime for the purpose of the Rome Statute and the crime’s existence under
customary international law.
120 US Proposed ‘Understandings’, circulated informally on 6 June 2010, on file with
121 Kress & von Holtzendorff, ‘The Kampala Compromise’, 1205.
122 Cf. Kress, ‘Time for Decision’, 1140 who somewhat curiously says the definition ‘goes
slightly beyond customary international law’, and that ‘there is no absolute clarity
about the applicable definition in customary international law and hence there is
some legitimate scope for “refining” and hereby “crystallizing” customary
international law’.
123 June 2006 SWGCA Report, [23]; January 2007 SWGCA Report, [18].
124 Article 22(1) provides that a person shall not be criminally responsible under this
Statute unless the conduct in question constitutes, at the time it takes place, a crime
within the jurisdiction of the Court.
125 Article 15(1) provides that ‘no one shall be guilty of any criminal offence on account of
any act or omission which did not constitute a criminal offence, under national or
international law, at the time when it was committed’. Consistent with the arguments
advanced in this chapter, paragraph (5) of Article 15 provides that ‘nothing in this
article shall prejudice the trial and punishment of any person for any act or omission
which, at the time when it was committed, was criminal according to the general
principles of law recognised by the community of nations’. International Covenant for
Civil and Political Rights, opened for signature 16 December 1966, 999 UNTS 171 (entered
into force 23 March 1976).
126 Article 34 of the VCLT provides that: ‘A treaty does not create either obligations or
rights for a third State without its consent.’ The dominant view is that Article 34 is not
otherwise violated by the Rome Statute’s extension to non-States Parties because it
does not in general create new obligations, rather it serves as a mechanism to enforce
existing rights. Consistent with the foregoing, an argument can be made out that the
Security Council does not have the power to subject the nationals of non-States Parties
under the Rome Statute to criminal jurisdiction in respect of acts that do not amount
to crimes under customary international law.
127 See Chapter 6, the subsection entitled ‘The applicability of Article 12(3)’.
128 Milanovic, ‘Aggression and Legality’, 171–175 reaches the same conclusion.
129 See for example: Randelzhofer, ‘Article 2(4)’, 121–122, 128; Schachter, ‘The Right of
States to Use Armed Force’, 1642; Arend & Beck, International Law, 84–88; Neff, War and
the Law of Nations, 362–365, 372–373; Ronzitti, ‘Use of Force’, 147; Antonio Tanca,
Foreign Armed Intervention in Internal Conflict, Dordrecht: Martinus Nijhoff Publishers,
1993; Tom J. Farer, ‘Harnessing Rogue Elephants: A Short Discourse on Foreign
Intervention in Civil Strife’ (1969) 82(3) Harvard Law Review 511; Deborah Z. Cass, ‘Re-
Thinking Self-Determination: A Critical Analysis of Current International Law
Theories’ (1992) 18 Syracuse Journal of International Law and Commerce 21; Schachter,
International Law, 114–115.
130 See for example: Schachter, ‘The Right of States to Use Armed Force’, 1629; Arend &
Beck, International Law, 129–134; Dinstein, War, Aggression and Self-Defence, 67; Thomas
M. Franck, ‘Humanitarian and Other Interventions’ (2005) 43 Columbia Journal of
Transnational Law 321, 324–328; Christopher C. Joyner, ‘“The Responsibility to Protect”:
Humanitarian Concern and the Lawfulness of Armed Intervention’ (2006–2007) 47
Virginia Journal of International Law 693, 700–703; Christine Gray, ‘From Unity to
Polarization: International Law and the Use of Force Against Iraq’ (2002) 13(1) European
Journal of International Law 1, 20; Michael Byers, ‘The Shifting Foundations of
International Law: A Decade of Forceful Measures Against Iraq’ (2002) 13(1) European
Journal of International Law 21, 28; Erika De Wet, ‘The Relationship Between the Security
Council and Regional Organisations During Enforcement Action under Chapter VII of
the United Nations Charter’ (2002) 71 Nordic Journal of International Law 1, 4;
Ademola Abass, ‘The New Collective Security Mechanism of ECOWAS: Innovation and
Problems’ (2000) 5(2) Journal of Conflict and Security Law 211; Nigel D. White, ‘On the
Brink of Lawlessness: The State of Collective Security Law’ (2002–2003) 13 Indiana
International and Comparative Law Review 237, 247; Ahmad M. Ajaj, ‘Humanitarian
Intervention: Second Reading of the Charter of the United Nations’ (1992–1993) 7
Arab Law Quarterly 215; Martha Brenfors & Marlene Maxe Petersen, ‘The Legality of
Unilateral Humanitarian Intervention – A Defence’ (2000) 69 Nordic Journal of
International Law 449; International Commission on Intervention and State
Sovereignty, The Responsibility to Protect (2001),
131 See for example: Randelzhofer, ‘Article 2(4)’, 132–133; Brownlie, International Law,
298–299; Arend & Beck, International Law, 103–110; Dinstein, War, Aggression and Self-
Defence, 181; Derek Bowett, ‘The Use of Force in the Protection of Nationals’ (1957) 43
Transactions of the Grotius Society 111, 111–126; Antonopoulos, ‘The Unilateral Use of
Force’, 130.
132 See for example: Roberto Barsotti, ‘Armed Reprisals’ in Cassese, The Current Legal
Regulation of the Use of Force, 79; Julius Stone, Legal Controls of International Conflict: A
Treatise on the Dynamics of Disputes and War-Law, Holmes Beach: Wm W. Gaunt & Sons,
1974, 286; Bothe, ‘War Crimes’, 387; Roda Mushkat, ‘Is War Ever Justifiable? A
Comparative Survey’ (1986–1987) 9 Loyola of Los Angeles International and Comparative Law
Review 227, 251–252.
133 See for example: Stone, Aggression and World Order, 43; M. Cherif Bassiouni, ‘The
Definition of Aggression in International Law: The Crime Against Peace’ in Bassiouni &
Nanda, A Treatise on International Criminal Law, vol. I, 159, 164; Randelzhofer, ‘Article 2
(4)’, 123; Brownlie, International Law, 265–266; Schachter, ‘The Right of States to Use
Armed Force’, 1632; McCoubrey & White, International Law, 25–26; Josef Mrazek,
‘Prohibition of the Use and Threat of Force: Self-Defence and Self-Help in International
Law’ (1989) 27 Canadian Yearbook of International Law 81, 87; Subhas C. Khare, Use of Force
Under UN Charter, New Delhi: Metropolitan Books, 1985, 40–41; Fernando R. Teson,
Humanitarian Intervention: An Inquiry into Law and Morality (2nd ed.), Irvington-on-
Hudson: Transnational Publishers, 1997, 150–154; McDougal & Feliciano, ‘Legal
Regulation of Resort to International Coercion’, 1101; Dinstein, War, Aggression and Self-
Defence, 82; Gordon, ‘Article 2(4)’, 276.
134 In relation to the scope of self-defence see Randelzhofer, ‘Article 51’; Dinstein, ‘A
Survey of Self-Defence’; Dinstein, War, Aggression and Self-Defence; Brownlie, International
Law; Schachter, ‘The Right of States to Use Armed Force’, 1620; Abraham D. Sofaer, ‘On
the Necessity of Pre-emption’ (2003) 14(2) European Journal of International Law 209;
Arend & Beck, International Law, passim; Franck, ‘Humanitarian and Other
Interventions’; Michael Bothe, ‘Terrorism and the Legality of Pre-emptive Force’ (2003)
14(2) European Journal of International Law 227; Mrazek, ‘Prohibition of the Use and
Threat of Force’; David Kaye, ‘Adjudicating Self-Defense: Discretion, Perception, and
the Resort to Force in International Law’ (2005–2006) 44 Columbia Journal of
Transnational Law 134; Khare, Use of Force; Bert V. A. Roling, ‘The Ban on the Use of Force
and the UN Charter’ in Cassese, The Current Legal Regulation of the Use of Force, 3; Cassese,
‘On Some Problematical Aspects’; Myres McDougal & Florentino Feliciano, Law and
Minimum World Public Order: The Legal Regulation of International Coercion, New Haven: Yale
University Press, 1961; Report of the Secretary-General’s High-Level Panel on Threats,
Challenges and Change, A More Secure World: Our Shared Responsibility, New York: United
Nations (2004), 63; The White House, The National Security Strategy of the United States of
America, Part V: Prevent Our Enemies from Threatening Us, Our Allies and Our Friends
with Weapons of Mass Destruction, available at
135 W. Michael Reisman, ‘Criteria for the Lawful Use of Force in International Law’
(1984–1985) 10 Yale Journal of International Law 279, 281. In the context of forcible
interventions, Stahn identifies a range of concepts that might be employed in the
course of an assessment, namely, justification, ex post validation, pardonable illegality
and legitimacy, in addition to the traditional categories of legality and illegality:
Carsten Stahn, ‘Enforcement of the Collective Will After Iraq’ (2003) 97 American
Journal of International Law 804, 819. See also Franck, ‘Humanitarian and Other
Interventions’, 325; Murphy, ‘Criminalizing Humanitarian Intervention’, 352 citing
Thomas M. Franck, Recourse to Force: State Action Against Threats and Armed Attacks (2002),
186; Murphy, ‘Protean Jus Ad Bellum’, 22. Murphy suggests that a range of factors can be
analysed to predict whether coercive behaviour is acceptable, including ‘(1) the degree
of coercion actually inflicted by State A upon State B or its nationals; (2) the gravity of
coercion that State A fears from State B; (3) the extent to which other States are
condoning State A’s coercion; (4) the pedigree of State B as a member of the
international community; (5) the degree to which State A’s coercion is tailored to
respond to the threat from State B; (6) the degree to which State A’s coercion has
adverse collateral consequences for other states or persons’ (at ibid., 45).
136 Rolf Einar Fife, ‘Criminalizing Individuals for Acts of Aggression Committed by States’
in Morten Bergsmo (ed.), Human Rights and Criminal Justice for the Downtrodden: Essays in
Honour of Asbjorn Eide, Leiden: Martinus Nijhoff, 2003, 53, 73; Kress, ‘The Crime of
Aggression Before the First Review Conference’, 859.
137 M. Cherif Bassiouni, Introduction to International Criminal Law, Ardsley: Transnational
Publishers Inc., 2003, 111.
138 Ibid., 29; Yoram Dinstein, ‘International Criminal Law’ (1985) 20 Israel Law Review 206,
221; Ilias Bantekas & Susan Nash, International Criminal Law (2nd edn), London:
Cavendish Publishing, 2003, 5; Cassese, International Criminal Law, 11–12.
139 In relation to war crimes see Bothe, ‘War Crimes’, 387.
140 Monica Hakimi, ‘To Condone or Condemn? Regional Enforcement Actions in the
Absence of Security Council Authorization’ (2007) 40 Vanderbilt Journal of Transnational
Law 643, 648.
141 Kress, ‘Time for Decision’, 1140.
142 Paulus, ‘Second Thoughts’, 1121.
143 Kress, ‘The Crime of Aggression Before the First Review Conference’, 859.
144 Robinson & Haque, ‘Advantaging Aggressors’, 50, make a similar point.
145 Barriga, ‘Against the Odds’, 1, 8–9.
146 Kress & von Holtzendorff, ‘The Kampala Compromise’, 1205.
147 A similar conclusion is reached by Creegan, ‘Justified Uses of Force’, 66, 81. Creegan
sees this as a reason not to criminalise aggression. I, on the other hand, view it as
merely highlighting the fact that a narrower definition would have been preferable.
148 Roger S. Clark, ‘Negotiating Provisions Defining the Crime of Aggression, its Elements
and the Conditions for ICC Exercise of Jurisdiction Over It’ (2009) 20(4) European Journal
of International Law 1103, 1110.
149 Article 21(1)(b).
150 Kress & von Holtzendorff, ‘The Kampala Compromise’, 1210–1211.
151 See further Chapter 7.



Mon 28 May 2018


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