To my shame, I’ve only just noticed that Ken Gallant in his excellent book The Principle of Legality in International and Comparative Criminal Law (Cambridge: Cambridge University Press, 2009) – recently reviewed in the JICJ here – addresses the difficult problem of applying the substantive law of the Rome Statute to situations in which the Court acquires jurisdiction over an individual only ex post facto, i.e. after the commission of the alleged crime, for example under a UNSC referral or on the basis of an Art. 12(3) declaration (pp. 337-343). If, for instance, Gaddafi were to be put on trial before the ICC, and bearing in mind that Libya was never a party to the Rome Statute, can he be prosecuted for crimes or under theories of liability that are specific to the Rome Statute, such as indirect perpetration, which do not reflect customary law? I’ve written about this problem in my JICJ articles on whether the Rome Statute is binding on individuals and on aggression and legality. Ken argues (pp. 342-343), and I fully agree, that:
The possible retroactive application of non-customary international criminal law, especially after a Security Council referral, is not an imaginary problem. Many of the framers of the ICC Statute sought a progressive development of international criminal law and procedure. Therefore, they did not necessarily limit their drafting of the criminal law of the statute to that which was customary international law. It is not self-evident that all of the crimes listed in the statute are customary international law crimes.
Some respected commentators have suggested that all of the crimes set forth in the ICC Statute automatically apply when the Security Council has referred a situation to the ICC. This would be inconsistent with the legality analysis both of the statute and of international human rights law and with fundamental rules of treaty law.
Schabas, for example, claims that such an application would be permissible because it is “foreseeable” that the court would attempt to apply the statute to such people. The problem with this argument is that the states adopting the ICC Statute have no authority to prescribe new criminal law either for non-ICC states or for persons with no relevant connection to any ICC state. The ICC Statute can apply to a national of a non-ICC state who commits a criminal act in, or with effect in, an ICC state, as an instance of territorial jurisdiction. The states adopting the ICC Statute could not make law to apply to someone who is wholly unconnected with any ICC state party, and whose allegedly criminal acts are unconnected with such a state party, unless the crime were a customary international law crime over which there is universal jurisdiction (which, by hypothesis, the crime here is not). Foreseeability in the sense of legality can include a development in the law of a jurisdiction with legitimate authority over a person. It cannot mean foreseeability that an international organization will later attempt to impose its prescriptive jurisdiction on a person over whom it has no legitimate authority.
Schabas argues that the application of new, non-customary crimes in the ICC Statute to such persons is acceptable by pointing out that aggressive war was effectively a new crime at Nuremberg. The problem with this argument is that international human rights law has changed since that time. The claim by the Nuremberg Tribunal that nullum crimen sine lege was, in international law, merely a principle of justice was true then but is not so now. Now it is a rule of customary international law and perhaps a jus cogens rule at that.