Economic activity continues during war. But what rules apply when US troops occupy Syrian oil fields? Who is responsible when multinational companies use minerals extracted by child labourers in war zones? This book examines how international law regulates the war economies that are at the heart of strategic competition between great powers and help sustain the irregular warfare in today's war zones. Drawing on advances in our understanding of the social and economic dynamics in war zones, this book identifies predation, a combination of violence and economic opportunity, as the core pathology of war economies. The author presents a framework for understanding the regulation of war economies based on the history of international law and existing norms of international humanitarian law, international criminal law, international human rights law and the law of international peace and security. War Economies and International Law concludes that the pathologies of predation in war demand answers based on an international regulatory strategy.