Principles of International Criminal Law has become one of the most influential textbooks in the field of international criminal justice. It offers a systematic and comprehensive analysis of the foundations and general principles of substantive international criminal law, including thorough discussion of its core crimes. It provides a detailed understanding of the general principles, sources, and evolution of international criminal law, demonstrating how it has developed, and how its application has changed. After establishing the general principles, the book assesses the four key international crimes as defined by the statute of the International Criminal Court: genocide, crimes against humanity, war crimes, and the crime of aggression. This new edition revises and updates work with developments in international criminal justice since 2009. It includes new material on the principle of culpability as one of the fundamental principles of international criminal law, the notion of terrorism as a crime under international law, the concept of direct participation in hostilities, the problem of so-called unlawful combatants, and the issue of targeted killings. The book retains its highly-acclaimed systematic approach and consistent methodology, making the book essential reading for both students and scholars of international criminal law, as well as for practitioners and judges working in the field.