Against the backdrop of energy markets that have radically changed in recent decades, this book offers an in-depth study of energy regulation in international trade law. The author seeks to clarify what we define as 'energy' in the context of the applicable international trade rules, and gives the reader a thorough analysis of the concepts, history and law of the various legal frameworks underpinning international energy trade. In addition, several case studies address the ongoing quest for energy security and show how the existing rules relate to some of the vast challenges that energy markets face today, notably the decentralisation and decarbonisation of energy markets.