A note on the evolution of the principle of legality in international criminal law

Abstract

A proper understanding of the role played so far by customary international law in international criminal law, as reflected in the case law of the ad hoc tribunals, as well as the reasons why customary international law has played such a relevant function in contrast to its role in national legal orders is essential to the understanding of the process of criminalisation at the international level. It is only when one realises the limits inherent in customary rules as to the development of penal norms and their inability to assure legal certainty, that one can understand why the drafters of the Rome Statute have decided to leave aside to an important extent the traditional system of sources in international criminal law and have given written norms a central role in the definition of the crimes and the penalties.