Transformation of Customary Law through ICC Practice

Abstract

Article 21 of the Rome Statute, in defining the applicable sources of law for the International Criminal Court (ICC), breaks with the practice of the ad hoc tribunals by treating customary international law as only a secondary authority. Nonetheless, customary international law still has an acknowledged role in ICC jurisprudence in filling lacunae in the Rome Statute and aiding in its interpretation. One can also predict other instances in which the application of customary international law will be required. It remains to be seen, however, whether the ICC's use of customary law will lead to that law's further fragmentation or whether that use will instead modify customary law to reflect the ICC Statute.