The Identification of Customary Rules in International Criminal Law

This paper aims to examine whether a different methodology has emerged to identify customary rules in the field of international criminal law. For this purpose, this paper briefly touches upon debates regarding customary law as a source and an interpretative aid of international criminal law. It then critically studies the identification methodology of customary law to seek whether a new approach deviating from the classic two-element (State practice and opinio juris) approach is emerging in academia. It also recapitulates some cases of international criminal tribunals to ascertain whether these tribunals have formed a distinct method for custom identification. Finally, it explores the unique characteristics and difficulties in identifying customary rules in international criminal law. It concludes that a different method has not been developed in academia or adopted by tribunals in practice to identify customary rules in international criminal law. The two-element approach still serves as guidance for custom-identification in general, but a flexible application of it is acceptable in specific cases. International practitioners should be cautious in the identification of customary rules in international criminal law, so as to prosecute and punish suspects of international crimes without endangering the principle of legality.