On the Crime of Aggression and the ICC in a Quasi-Westphalian System

Ayla Prentice-Cuntz, Law & Policy
Katie Flannery, Program Director

In 1998, the negotiating parties in Rome equipped the International Criminal Court (ICC) with jurisdiction over four international crimes in its establishing treaty, the Rome Statute: crimes against humanity, war crimes, genocide, and the highly debated crime of aggression. Jurisdiction over the crime of aggression was made subject to further negotiations, since no consensus could be reached on its definition in the Rome Statute. In June 2010, the Assembly of States Parties (ASP) convened in the Ugandan capitol of Kampala in an effort to define the crime of aggression. At the conference, the States Parties adopted a definition to be included in the Rome Statute as Article 8 bis, if it is ratified by 30 States Parties and thereafter approved by a two-thirds majority vote to activate the ICC’s jurisdiction. These proposed amendments to the Rome Statute are known as the Kampala Amendments.

However, 16 years after the inclusion of the crime of aggression in the Rome Statute, States are still debating whether and how to activate the Court’s jurisdiction over it. What is it about the crime of aggression that makes it such a critical issue for the Court? Has the crime of aggression become a “lightning rod” for broader push back against the ICC?

What is the Crime of Aggression?

The Nuremburg Tribunal was the first court to prosecute for crimes against peace—the equivalent of today’s crime of aggression. In 1947, the Nuremburg Judgment decried aggression as “the supreme international crime, differing only from other crimes in that it contains within itself the accumulated evil of the whole.” Since the use of force by one State against another is generally prohibited under Article 2(4) of the UN Charter, [1] an act of aggression historically triggered State responsibility. However, the Nuremberg Tribunal’s prosecution for crimes against peace for the first time triggered individual criminal responsibility for a political or military leader for an act that otherwise normally falls under the principles of jus ad bellum—that is, the branch of international law governing the conditions under which States may legally resort to war. [2]

In 1974, the General Assembly adopted Resolution 3314, in which it defined an act of aggression as “the use of armed force by a State against the sovereignty, territorial integrity or political independence of another State, or in any other manner inconsistent with the Charter of the United Nations.” The Kampala Amendments’ proffered definition for the acts underlying the crime of aggression at the ICC mirrors the language of Resolution 3314, and also adds the additional element that the act constitute “a manifest violation of the Charter of the United Nations.” To complete the criminal act of aggression under the Kampala Amendments, an individual must plan, prepare, or initiate one of the enumerated acts, with knowledge of the circumstances establishing the act of aggression.

Responses to the Activation of the Crime of Aggression

The crime of aggression has proved to be a sensitive topic and difficult to define, in part because the definition has political and military repercussions for States. In fact, some States reject the idea of individual criminal responsibility for aggression altogether. [3] While a considerable number of the participants at the Kampala Conference supported the criminalization of acts of aggression, concerns about the relationship between the Court and the UN Security Council, the relationship between the crime of aggression and the other existing international crimes, [4] and the elements of the proposed amendments were expressed. [5]

Politicization of the Court

One of the main arguments articulated against crime of aggression jurisdiction is that of politicization. The ICC has often found itself in situations in which it had to defend itself against accusations of being politicized. What does politicization of the Court mean? A politicized court is one that bases its decisions on States’ national interests and follows political decisions. [6] Proponents of this argument claim that the crime of aggression is “of clearly marked political character” because it cannot be committed by an individual without the State also committing an act of aggression —and the decision by States to use force is itself political. [7] States have also expressed that the Kampala Amendments could deter legitimate military and self-defense operations to protect national interests. [8]

Security Council Determination of an Act of Aggression

One of the mechanisms conferring jurisdiction on the ICC for an act of aggression is provided for in Article 15 bis of the Kampala Amendments. Effectively, this provision provides that the ICC Prosecutor may investigate an act of aggression regardless of a Security Council finding of aggression at the State level, unless the Security Council defers the investigation under Article 16. Although the Prosecutor is expected to give the Security Council an opportunity to speak first on the issue, a UNSC determination is not binding for the Court’s purposes. The Prosecutor’s ability to investigate independently from a UNSC determination concerns a number of States deeply, which is why “compromises” like the one proposed by the United States have emerged: the United States is willing to accept the Kampala Amendments if the Security Council is, in turn, vested with the power to block any prosecution of a crime of aggression. In practice, this would mean effective immunity for the five permanent members of the Security Council (United States, China, Russia, France, and Britain) due to their power to veto any decision that is harmful to themselves or their allies.

Sovereignty and Resistance to the ICC

In addition to the pointed criticism over the inclusion of the crime of aggression, the ICC has been accused of functioning with “insufficient checks and balances” and “insufficient protection against politicized prosecutions,” and of showing symptoms of Western imperialism. However, in light of the foregoing discussion, the primary arguments brought against the ICC by a number of States may be grouped together as challenges that are based on a belief in the ICC’s irreconcilable co-existence with the concept of State sovereignty.

State sovereignty is the hallmark of the international world order known as the “Westphalian system,” beginning in 1648 with the Peace of Westphalia that ended the Thirty Years’ War. The Westphalian system introduced the concept of equal, autonomous States and the presumption against external interference. This new concept guaranteed rulers the absolute authority to regulate their domestic affairs. This theory dominated the field of international relations for several centuries, and in many ways continues to exert deep influence—in fact, the Westphalian affirmation of sovereign equality is listed as the very first principle of the United Nations, in Article 2(1) of the UN Charter.

While the rejection of foreign interference in domestic affairs was once a very rigid principle, the idea of individual criminal responsibility for State officials under international law had already emerged in some form by the early twentieth century,[9] thus robbing the Westphalian system of some of its initial strictness. More examples of the paradigm’s loosened influence include the development of the universal jurisdiction doctrine and the creation of the UN Security Council. Universal jurisdiction refers to every State’s power to prosecute for international crimes regardless of any recognized linking point between the crime and the prosecuting State, and therefore threatens the principle of non-intervention in a State’s domestic affairs. Similarly, the Security Council has the power under Chapter VII of the UN Charter to authorize foreign military intervention in a State, further eroding the foundation of the Westphalian system.

Although we have clearly moved beyond a purely Westphalian world order, the system in many ways continues to exert deep influence over fears and skepticisms of international institutions. The ICC is no exception: while the idea of an international criminal tribunal in a Westphalian system is not wholly absurd (after all, the ICC is still fundamentally rooted in State sovereignty, since States had to ratify the Rome Statute in the first place to bring the Court into existence), many of the Court’s most vocal opponents have their ideological roots firmly in the Westphalian system.

The Crime of Aggression in Context of the Pushback against the ICC

Where States are nervous about the operation of the Court inside its territory and against its citizens, the ongoing debate about the crime of aggression provides an opportunity to give full voice to critiques of the ICC. This is not as acceptable in discussions on the other crimes constituting the Court’s jurisdiction, which are bolstered by stronger consensus in the international community.

The challenge with reconciling the crime of aggression and classic, Westphalian-style sovereignty is that prosecutions for aggression would permit ICC prosecution of State officials whose activities are, by implication, acts of States themselves. States want to retain their authority over domestic affairs and the exclusive power to determine when to resort to armed force. The argument of State sovereignty is not a new one. On the contrary: States have used the concept of sovereignty for centuries as an excuse to opt out of certain treaty provisions that have pushed the envelope. [10]

However, although a supranational institution like the ICC seems, prima facie, to strip States of their sovereignty, the inclusion of the crime of aggression would actually re-emphasize the traditional Westphalian norm of non-intervention and the UN Charter norm of non-use of force: by adding another possible punishment for intervening in other States’ domestic affairs, ICC jurisdiction over aggression would thus arguably deter States from—and therefore protect the general principle of non-intervention and from using unlawful force against another State.


The Westphalian system has become a tool to be discarded or used as a shield against the ICC by States. Nevertheless, it seems that in the name of human rights and the struggle against impunity, States have generally proved willing to depart from the rigid Westphalian system for genocide, crimes against humanity, and war crimes. However, the political and fundamentally State-centric nature of war makes the crime of aggression a harder question. Many States are reluctant to give up, even partly, their rights under the principle of sovereignty when it comes to warfare.

If, as the Nuremburg Judgment said decades ago, the crime of aggression truly does “contain[] within itself the accumulated evil of the whole,” then increased resistance from States around aggression may signal an unwillingness by some to depart from the Westphalian system in the ways necessary to properly equip an international court like the ICC.

1. Exceptions to this rule are either the use of force as self-defense under UN Charter Article 51 or an authorization by the UN Security Council under UN Charter Article 42.
2. Ian Henderson, The Contemporary Law of Targeting 3 (2009).
3. Colonel Stuart W. Risch, Hostile Outsider or Influential Insider? The United States and the International Criminal Court, 432 Army Lawyer 61, 76 (2009).
4. See, e.g., Statement by Norway (expressing that the Court should prioritize genocide, crimes against humanity, and war crimes because investigations concerning crimes of aggression would be “extremely resource consuming”) at the Kampala Conference (2010), available at http://www.icc-cpi.int/iccdocs/asp_docs/ASP9/OR/RC-11-Annexes-ENG.pdf.
5. See, e.g., Statement by Cuba (voicing concerns that the Court would qualify the definition’s element of a “manifest violation” of the UN Charter “with the usual subjective factor”) at the Kampala Conference (2010), available at http://www.icc-cpi.int/iccdocs/asp_docs/ASP9/OR/RC-11-Annexes-ENG.pdf.
6. Gerry Simpson, Politics, Sovereignty, Remembrance, in The Permanent International Criminal Court: Legal and Policy Issues 471, Dominic McGoldrick, Peter Rowe, & Eric Donnelly (eds.) (2004).
7. Erin Creegan, Justified Uses of Force and the Crime of Aggression, 10 J. Int’l Crim. Just. 59, 59 (2012).
8. E.g., US Delegate Intervention, ‘Into the Homestretch: Towards the Activation of the Kampala Amendments on the Crime of Aggression’ Interactive Panel Discussion on the Occasion of the Day of International Criminal Justice (2014).
9. See e.g. the International Agreement for the Suppression of White Slave Traffic 1904 or the Treaty of Versailles 1919, Article 227.
10. A good example is the reservations made to the International Court of Justice’s (ICJ) jurisdiction.

Photo credit: UN Photo/Stuart Price

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