The Role of Customary Law in the Statute of the International Criminal Court

This paper deals with the role of customary law as a basis for establishing individual criminal responsibility in the Statute of the International Criminal Court (ICCS). Firstly, it analyses the place of customary law among the ICCS's legal sources. Secondly, it specifically investigates whether a prohibition against the use of customary law as a basis for establishing criminal responsibility of individuals can be derived from the ICCS. To this purpose, it examines the scope of the principle of legality and its relationship with customary law in the ICC system. Thirdly, it takes up the question as to whether the ICCS allows for the use of customary law as a criterion of interpretation, even against the accused. Finally, it deals with the proposal to resort to customary law to ground criminal responsibility in cases when the ICC exercises jurisdiction over crimes allegedly committed on the territory or by nationals of non-States Parties. The paper concludes that the role of customary law in the ICCS is marginal and, in any case, minor than it had in previous experiences of international criminal law. However, it also shows that there is still some place for resorting to customary law even in issues regarding criminal liability.