What a positively weird question, you might think. The Rome Statute of the International Criminal Court cannot be binding on individuals. It is a treaty, to which only states can be parties, since individuals are not subjects of international law, and it is furthermore a general principle of international law that treaties cannot bind non-parties. This is the answer that public international lawyers would give almost by reflex.
But what if the question was put in slightly different terms — are the provisions of the Rome Statute that define international crimes and forms of individual responsibility substantive or jurisdictional in nature? Do they, in other words, define when an individual is criminally responsible, or do they only say when the Court can establish jurisdiction for the individual’s violation of a norm emanating from a different source of international law, such as custom? Many of us, particularly those with a more of a criminal law background, would be tempted to say that of course the provisions of the Rome Statute must be substantive in nature, since one of the purpose of the Statute was precisely to get away from vague and indeterminate inquiries into custom. But if that is true, then the Statute — a treaty — must be binding on individuals who have never consented to be bound by it, nor could have done so.
But why does this matter? If the Statute is only jurisdictional in nature, as have incidentally been the statutes of all other international criminal courts and tribunals so far (at least nominally), then the source of substantive norms of criminal law binding on individuals must be elsewhere, primarily in customary law. If this is so, then the Statute could never go beyond customary law, and any individual accused before the Court will at least in principle have to be able to mount a challenge as to whether the charges against him have a basis in customary law. If, on the other hand, the Statute is seen as being substantive in nature, then it may well go beyond customary law, but it would arguably run afoul of the nullum crimen sine lege principle in at least two cases — when a particular situation has been referred to the Court by the UN Security Council or by a non-state party — since the supposedly substantive Statute would not have been binding on the individuals concerned at the time that they allegedly committed their offense.
Let me put this in less abstract terms. When militia under Sudanese control committed mass atrocities in Darfur, were they violating custom or the Rome Statute, to which Sudan is not a party? And if the answer is the former, could they be prosecuted before the ICC under UNSC referral even for those crimes which may not be customary in nature but are nonetheless in the Statute, or under theories of responsibility which are almost definitely not customary? Can, for example, Omar Al-Bashir, the President of Sudan, (if ever tried) be held responsible under a theory of indirect perpetration or perpetration by means, which has never been used in any other international criminal tribunal? Would this not violate the principle of legality, as the Rome Statute did not extend to the territory of Sudan at the time the alleged offenses were committed?
I explore these and other issues, such as when, why and how treaties can directly bind individuals without the mediation of domestic law, and the options that the Court will have in addressing challenges to charges based on the nullum crimen principle, in an article forthcoming in the Journal of International Criminal Justice. A pre-print draft is now available on SSRN, and any comments from our readers would be greatly appreciated.