The Principle of Legality and the Role of Customary International Law in the Interpretation of the ICC Statute

This article endeavours to determine the role of customary international law in the prosecution of crimes under the jurisdiction of the ICC. In its first findings dealing with the meaning of Article 21(b) of the ICC Statute, the Court has attributed to customary international law the subsidiary role of filling the lacunae of the Statute. This interpretation seems to admit, although in a limited and imprecise way, an application of customary international law in the proceedings before the Court. However, the principle of legality, as perceived in the ICC Statute, appears to limit the recourse to customary international law to the interpretation of written rules. Moreover, an analysis of relevant Articles of the Rome Statute, in which an application of customary rules could be, or has been, invoked, discloses the different shapes that the potential interpretative resort to customary law in determining the meaning of the statutory provisions might take.