“We should entrust criminal law with the defense of international peace and universal order, a task neither diplomacy nor the politics of the League of Nations were able to carry.” This was the view of the former professor of criminal law at the University of Geneva, Jean Graven, after he attended the Nuremberg Trial. Originally a criminal lawyer, he supported the idea of international criminal law through its dissemination and teaching from 1948 onwards. Among good examples of his efforts are his course on crimes against humanity before The Hague Academy; a course of international criminal law he taught in Geneva but also in Teheran and Cairo; and his draft of the Ethiopian criminal code in which he tried to implement international crimes.  As a broker of the idea of an ideal international criminal law, Jean Graven did not address the criticisms levelled against Nuremberg. He rather stood firm by its fundamental idea: the fight for a common concern of humankind. The unpublished documents in his personal library support this assertion.