This book aims at introducing an aspect of the legal thought of Hans Kelsen, and more particularly its conception of International Law (its evolution an its nature). The originality of this research results from the integration of two translations of under-studied texts of Kelsen concerning the International criminal justice during the creation of military tribunals post WWII. It allows to observe how the thought of Kelsen is built but also shows the limits of his normativism on an international scale because the interstate structure does not disappear completely. It entails an adjustement based, in particular, on recogntion of the individual as litigant.