Understanding the global security environment and delivering the necessary governance responses is a central challenge of the twenty-first century. On a global scale, the central regulatory tool for such responses is public international law. But what is the state, role, and relevance of public international law in today’s complex and highly dynamic global security environment? The Oxford Handbook of the International Law of Global Security provides a groundbreaking overview of the relationship between international law and global security. It constitutes a comprehensive and systematic mapping of the various sub-fields of international law dealing with global security challenges, and offers authoritative guidance on key trends and debates around the relationship between public international law and global security governance. The Handbook features original contributions by leading scholars and practitioners from a wide range of professional and disciplinary backgrounds, reflecting the fluidity of the concept of global security and the diversity of scholarship in this area.