This book discusses the multilayered legal structures concerning the regulation of crimes under international law. It covers both core crimes and other types of crime under international law, and examines relevant substantive and procedural rules alike. Pursuing such a comprehensive approach is essential to understanding the basic frameworks of international criminal law, since the varied perspectives on international crimes are connected to different systems of enforcement. Being aware of this interrelatedness is conducive to an in-depth examination of individual topics in both substantive and procedural aspects. On the basis of such an inquiry, this book concisely provides a systematic overview of international criminal law.