The International Court of Justice and the Concept of Aggression: Lessons for the ICC?

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Cross-posted from EJIL: Talk!

The Kampala Amendments to the Statute of the International Criminal Court (ICC) adopted in June 2010 define the crime of aggression for the purposes of the ICC Statute and set out the conditions under which the ICC will exercise jurisdiction with respect to that crime. It was decided in Kampala that the aggression amendments will only become operational, in the sense that the ICC can only exercise jurisdiction over the crime of aggression: (i) one year after the aggression amendments have come into force for at least 30 States and (ii) if the ICC Assembly of State Parties adopts a further decision to activate that jurisdiction, with 1 January 2017 being the earliest date for the adoption of that decision [Arts. 15 bis (2) & (3) & 15ter (2) & (3), ICC Statute]. Given that 23 states have now ratified or accepted the aggression amendments and that 1 January 2017 is under 18 months away, the activation of the ICC’s jurisdiction over the crime of aggression is not very far away at all [see this report on action by other states considering ratification]. As that moment – when the ICC is able to exercise jurisdiction  over aggression approaches – attention will turn (back) to a couple of issues that remain unresolved with respect to the interpretation of the Kampala amendments. One of those issues is whether the Court will be entitled to exercise jurisdiction over the nationals of a party to the Rome Statute which has not accepted the aggression amendments but which is alleged to have committed aggression on the territory of a state party that has ratified or accepted those amendments (see previous discussion here & here). The second issue is the interpretation to be given to the definition of the crime of aggression under the Kampala amendments.

Article 8 bis(1), of the ICC Statute provides that: “For the purpose of this Statute, “crime of aggression” means 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, of an act of aggression which, by its character, gravity and scale, constitutes a manifest violation of the Charter of the United Nations”.

The relationship between the concept of the “crime of aggression” and of “act of aggression” under the ICC Statute and under general international law respectively remains unclear. Under the Kampala amendment only an “act of aggression” which “by character, gravity and scale, constitutes a manifest violation of the Charter of the United Nations” can amount to the “crime of aggression” attracting individual criminal responsibility. Despite attempts in interpretive Understandings adopted in Kampala to give guidance with respect to the definition of the crime, the ICC will have its work cut out in establishing what amounts to a manifest violation of the UN Charter such that it should be regarded as the crime of aggression.

As the concept of aggression is one which relates not merely to individual criminal responsibility but builds on state responsibility for unlawful uses of force, it is instructive to examine how the International Court of Justice (ICJ) has dealt with the concept of aggression. The ICJ has never made a finding that a states has committed an act of aggression. However, it has in cases dealing with the use of force relied explicitly (Nicaragua and Armed Activities cases) or implicitly (Oil Platforms case) and quite significantly on the Definition of Aggression in General Assembly Resolution 3314. This is the same resolution that is adopted in Article 8bis(2) of the amended Rome Statute in defining an act of aggression. Furthermore, just as there are gradations of aggression in the Kampala amendments, the ICJ has also developed gradations of the use of force which might, or might not, be useful in examining the meaning to be given to each of the different grades of aggression relevant to the ICJ.

In a recent paper to be published in a volume on aggression edited by Claus Kreß and Stefan Barriga (two key players in the drafting and adoption of the Kampala amendments), we review the contribution of the ICJ in defining the concept of aggression against the background of the Kampala Amendments. We argue that the ICJ has influenced the gradation of the concept of aggression by drawing an implicit parallel with the concept of “armed attack”. We argue in particular that the jurisprudence of the ICJ suggests that there are two different sets of concepts which allow gradation of the use of force, through an assessment of the gravity of the force used. In our conclusion, we say that:

One set is that which progresses from a mere use of force (article 2(4) UN Charter), to an armed attack (article 51, UN Charter), to a serious breach of a peremptory norm of general international law (article 40, Articles on State Responsibility). Another set is that which moves from a mere use of force, to an act of aggression, and then to a war and/or crime of aggression. The first set of concepts is used exclusively in the realm of state responsibility, whereas the second set doubles as one that can serve both for the purposes of state responsibility, and for the purposes of individual criminal responsibility. What this means is that both sets have been used, at least by the International Court of Justice, to discuss the responsibility of states for use of force, but the second set has also been used by the IMT (International Military Tribunal at Nuremberg], the GA [the General Assembly], and the drafters of the Kampala amendments, in order to define the crime of aggression as a crime entailing individual criminal responsibility.

As can be seen, each of those sets has three steps or grades in it. The key question is whether these sets run in parallel such that each step or grade in one set is to be regarded as equivalent to the corresponding step or grade in the other set. In our paper, we discuss the interaction and potential relationship between these sets and grades. We show from the jurisprudence of the ICJ that the concept of armed attack seems to correspond more closely, even if not precisely, to an act of aggression.


Antonio Tzanakopoulos is Associate Professor of Public International Law, University of Oxford & Secretary-General of the International Law Association.