Backgrounder on Aggression

By Brendan Naef

The crime of aggression is the hot topic at the Review Conference this week, and perhaps right up to final moments on Friday. Discussion has focused on the definition of the crime and its constitutive elements, and also, more controversially, the jurisdictional conditions of its enforcement. Otherwise stated, the conference are discussing what the State Parties believe “aggression” to be and the situations in which individuals accused of the act may fall within the grasp of the International Criminal Court. By no means, however, should this discussion be taken as an indication that the execution of a war of aggression is not yet an international crime. Simply put, although the current lack of agreement among States over a specific or exhaustive definition of the act may significantly complicate matters, in no way does it provide that perpetrators of aggression cannot be prosecuted. Thus, the role of the State Parties to the Rome Statute is to come to an agreement on aggression that falls within the boundaries of the current customary law definition. In the following discussion I will briefly address some of the past efforts to define the act of aggression, and I will follow this with a review of some of the aspects likely to be considered in Kampala.

It is perhaps paradoxical that the crime of aggression, labelled as the supreme international crime by the ad hoc International Military Tribunal (IMT) following WWII and listed as one of “the most serious crimes of concern to the international community” in the Rome Statute, continues to be the at the root of important debate at the ICC and in international law in general. This “supreme” crime, after all, is by no measure new. In fact, it was used to prosecute individuals far before the often-quoted benchmark year of 1946 (Paust et al. include an interesting list of examples in International Criminal Law: Cases and Materials, 2007, such as the 1818 Congress of Aix-La-Chapelle where the decision was made to detain Napoleon for initiating wars against peace.).

What is it, then, that makes the legal definition of aggression so difficult to grasp as compared to genocide, crimes against humanity, or war crimes? The answer lies in the simple fact that States behave differently and the varying interpretations of aggression can either assist or hinder this behaviour to different degrees.  Thus, in general, interventionist leaning States support more restrained or restricted definitions of aggression while traditionally non-interventionist States lobby for broader definitions. The stalemate created by the differing opinions is buttressed by the simple fact that an absence of a concrete definition doesn’t seem to bother powerful States.

Putting aside the political aspects in order to focus on the legal, the passage of time has contributed to a gradual refining of the definition of aggression. The following are among the most significant events in the development of the definition:

  • Among the acts listed as triggering individual criminal liability in the London Agreement of 8 August 1945 establishing the IMT was the “planning, preparation, initiation or waging of a war of aggression”.  The United Nations General Assembly (UN GA) subsequently affirmed both the criminal law principles of the IMT Charter as well as the Tribunal’s judgments;
  • Following the work of UN Special Committees over a period of 20 years, in 1974 the UN GA adopted Resolution 3314 (XXIX) in which it elaborated the definition of the crime while leaving a significant amount of discretion to the Security Council (UN SC) to determine additional forms of aggression;
  • Although the definition propounded by the UN GA in 3314 was not perfect, it was in part confirmed by the International Court of Justice in the Nicaragua decision of 1986 where the Court underlined that “sending into another State armed bands with the task of engaging in armed act” (as described in Article 3(g) of resolution 3314) constituted aggression under international customary law.  Arguably among the most well-known of the ICJ decisions, the case contemplated the US support for the Contra guerrillas, who were fighting a decade-long rebellion, as well as the US mining of Nicaraguan harbours.  After losing its argument contesting the Court’s jurisdiction, the United States withdrew all participation in the case.  Although the ICJ awarded reparations to Nicaragua, the US ultimately used its position as a permanent member of the Security Council to veto attempts to enforce the judgment;
  • Finally, in 1996 the International Law Commission adopted a Draft Code of Crimes Against Peace and Security of Mankind in which it detailed individual criminal responsibility for the individual who leads, plans, or participates, inter alia, in the waging of aggression by a State.

The Review Conference and the Working Groups therefore have much to work with and will likely, at the very least, further refine the results of the above efforts. The Conference has addressed the actual definition of the crime of aggression, the conditions under which the Court’s jurisdiction will be triggered, and the specific elements of the crime. Within these topics, the States Parties have to discuss the issue of the ‘threshold’ needed for an act of aggression to constitute a violation of the UN Charter. The interplay between the launch of an investigation by the ICC Prosecutor and the determination of the existence of aggression by the UN SC must also be addressed. Several alternatives have been advanced for this matter including the proposal that no investigation occur without a previous declaration of aggression by the UN SC or that the ICC may proceed where there has been no UN SC determination after 6 months. Finally, the Conference is considering important jurisdictional issues surrounding the aggressor State and the acceptance of the Court’s jurisdiction.  For instance, whether or not the victim State’s acceptance of ICC jurisdiction should be sufficient to allow the Prosecutor to investigate alleged aggression or whether the aggressor State will have needed to have previously accepted ICC jurisdiction is a much debated issue (as detailed in other posts on this blog).

The events listed above demonstrate that, should a definition of the crime of aggression emerge from the conference in Kampala, it ought not be viewed in isolation. A revised Court statute with a complete definition of aggression, regardless of whether jurisdictional issues are agreed upon, will provide yet another important indicator of the presence of a customary prohibition of aggression and, as mentioned, will contribute to the refining of the definition.  Thus, although the definition may not end up affecting non-State Parties to the Rome Statute directly, it could nevertheless touch all States through its contribution to customary law.

At the same time, a word of caution must nevertheless temper any premature optimism towards the existence of a more robust and detailed definition of aggression in customary law: as first year international law students are routinely reminded, customary law develops through State practise (the repeated actions of States over time) and opinio juris (States feeling obligated to act in a certain manner). Accordingly, the manner in which powerful non-State Parties to the Rome Statute such as the United States, Russia, and China behave in the near future could conceivably keep any concrete definition of the prohibition of aggression at bay as far as customary law is concerned.


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