The Sadly Neutered Crime of Aggression

The Sadly Neutered Crime of Aggression

I’ve long supported providing the ICC with jurisdiction over the crime of aggression.  Call me old-fashioned, but I believe there is a great deal of truth to the IMT’s insistence that “[t]o initiate a war of aggression… is not only an international crime; it is the supreme international crime differing only from other war crimes in that it contains within itself the accumulated evil of the whole.”  We cannot collapse the distinction between the jus ad bellum and the jus in bello, but it is no doubt true that war crimes and crimes against humanity are particularly likely to be committed in the context of an illegal war.  (See, e.g., Iraq.)  Prevent the illegal war, you prevent the subsequent crimes.

The good news: the Review Conference has adopted a definition of aggression.  The bad news: the conditions governing the exercise of jurisdiction make it very unlikely that any significant act of aggression will ever be prosecuted.  Here is the relevant paragraph, 15 bis, concerning non-Security Council referrals:

4. The Court may, in accordance with article 12, exercise jurisdiction over a crime of aggression, arising from an act of aggression committed by a State Party, unless that State Party has previously declared that it does not accept such jurisdiction by lodging a declaration with the Registrar. The withdrawal of such a declaration may be effected at any time and shall be considered by the State Party within three years.

5. In respect of a State that is not a party to this Statute, the Court shall not exercise its jurisdiction over the crime of aggression when committed by that State’s nationals or on its territory.

This is, to say the least, a very restrictive provision.  The following chart explains when the ICC will have jurisdiction over an act of aggression.  The two actors refer to the state committing aggression (state of nationality) and the state against whom aggression is committed (territorial state). “OO” refers to a State Party that has opted out of jurisdiction.

  • State Party & State Party —–> Jurisdiction
  • State Party & State Party OO —–> Jurisdiction
  • State Party & Non-State Party —–> No Jurisdiction
  • State Party OO & State Party —–> No Jurisdiction
  • State Party OO & State Party OO —–> No Jurisdiction
  • State Party OO & Non-State Party —–> No Jurisdiction
  • Non-State Party & State Party —–> No Jurisdiction
  • Non-State Party & State Party OO —–> No Jurisdiction
  • Non-State Party & Non-State Party —–> No Jurisdiction

In other words, the ICC will only have jurisdiction over an act of aggression committed by a State Party who has accepted (by omission) that jurisdiction and only when that act is committed against a State Party.

There are a number of problems with this jurisdictional regime, which deviates substantially from the regime that governs the other crimes within the ICC’s jurisdiction.  First, the Court will have no jurisdiction over a State Party’s act of aggression against a non-State Party, even though it would have jurisdiction over war crimes and crimes against humanity committed as a result of that act.  That is an unfortunate asymmetry.

Second, it permits States Parties to take an a la carte approach to the ICC’s jurisdiction.  I could be wrong, but I find it unlikely that any state that routinely uses force against other states (or against non-state actors located in other states) will not opt out of aggression.  Why wouldn’t they?  There may be some reputation cost for a state not to be a part of the ICC, but it is difficult to believe that there will be any such cost for a state that joins the ICC but limits the Court’s jurisdiction over it to war crimes, crimes against humanity, and genocide.  The ICC’s jurisdiction over aggression will thus almost certainly be limited to states that do not have either the motive or the wherewithal to commit the crime in the first place.  (To be fair, the opt out provision does eliminate a possible disincentive for a state to join the ICC, which is a good thing.)

Third — and this is a serious problem — it permits States Parties to take a completely hypocritical approach to aggression.  As the chart indicates, a State Party that opts out of aggression cannot be prosecuted if it commits an act of aggression against a State Party that has not opted out.  But the converse is not true: States Parties that have not opted out could be prosecuted for acts of aggression against an opting-out State Party.  An opting-out State Party is thus protected against aggression by other States Parties but is permitted to commit acts of aggression itself, even against States Parties that have not opted out.  If anyone can think of a principled rationale for such asymmetry, let me know.

Fourth, and finally, the ICC will not have jurisdiction over a non-State Party that commits an act of aggression against a State Party, even though the Rome Statute specifically provides such territorial jurisdiction for war crimes, crimes against humanity, and genocide.  Perhaps that concession was necessary to gain the support of some States Parties, although I don’t understand why a State Party (opt in or opt out) would want to deprive the ICC of jurisdiction over an act of aggression committed against itself by a non-State Party.  But I do not see any legal rationale for the limitation.  Dapo Akande has argued that aggression is different than the other crimes in terms of the territorial state’s right under international law to transfer its jurisdiction to an international tribunal.  I rarely disagree with Dapo — and I feel great trepidation when I do.  But I disagree with him here.  It’s a complicated argument, one that I hope to discuss in a later post.  Suffice it to say for now (perhaps) that I don’t believe that applying normal principles of territorial jurisdiction to the crime of aggression would require the Court to adjudicate the “the rights or responsibilities of a non-consenting and absent third State” any more, or any differently, than it already does for a crime against humanity involving a non-Party state agent.  After all, just as the crime of aggression requires proof that a state engaged in an act of aggression, a crime against humanity requires proof that the crime took place “pursuant to or in furtherance of a State or organizational policy to commit such attack.”

You will hear many voices in the coming weeks praising the Review Conference for breaking the Security Council’s stranglehold on determining whether an act of aggression has occurred.  There is more than a grain of truth to that; it is indeed important that the ICC will decide that issue for itself in situations within its jurisdiction.  But the “within its jurisdiction” qualification is important.  As the above discussion indicates, it is an open question how many acts of aggression the ICC will ever have the opportunity to adjudicate.

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Marko Milanovic
Marko Milanovic


I agree with much of what you say. However, we should also note that under Art. 15 ter the Security Council can refer a crime of aggression to the Court even if it was committed by or on the territory of a non-state party, or a state party which has opted out. Now, of course, the very powerful and the friends of the very powerful will never be prosecuted under such a referral, but still – there is a mechanism that can to an extent alleviate the asymmetry that you point out.

Btw, Bill has complied a text of the actual amendments (though this is not the official final version):


Thank you for the nice summary. I just have one point. It seems to me that it is not that clear that in your scenario 3 the ICC wont have jurisdiction. You probably interpret it from para. 5 of Art. 15bis that reads: In respect of a State that is not a party to this Statute, the Court shall not
exercise its jurisdiction over the crime of aggression when committed by that State’s nationals or on its territory.

But is it all that clear what it means to commit the crime on the territory of a non-state party? Certainly the effects are felt there but was not the aggression planned and controlled from a state party?


Thanks, Kevin – this is helpful indeed. My guess is that the definition will be more useful in domestic litigation and discourse than before the ICC, at least for a while. At this point, it is more and more difficult for people to continue arguing that the international community cannot agree on a definition for the crime of aggression. 111 country did not disagree on this text (stating that 111 countries actually agreed on it appears somewhat of an overstatement…) – and many more (including the likes of Iran) do not dislike this definition too much. After Nuremberg, this is a very good development….despite the fact that it will remain on the books only for the next few years…

Tamás Hoffmann
Tamás Hoffmann


I agree with every word of your comment.
However, it might be useful to discuss the apparently uncontroversial definition itself because for me it is a real departure from customary law and seems to be based on a confusion of act of aggression with the crime of aggression.

The ICC amendment takes as a point of departure Res. 3314, which however only gives an exemplificative definition of act of aggression and clearly separates it from war of aggression as an international crime. The ICC definition collapses this distinction and only adds to the confusion surrounding the limits of use of force by using the language ‘manifest violation of the Charter of the United Nations’.

I simply cannot imagine how could judges of the ICC, usually possessing only basic knowledge of public international law resolve issues such as the legality of anticipatory self-defence, protection of nationals, title to territory etc.


Well, who actually gets to determine when a war is illegal or legal?


Joe asks a good question: Who determines the legality of a war? Congress authorized U.S. invasion and occupation of Iraq, making the Iraq war legal under the U.S. Constitution. Are you suggesting that the U.S. surrender its war-making authority to an international body? Why not surrender our sovereignty to the UN mob, and be done with it?