The second edition of this concise and well-loved textbook has been enhanced and developed while continuing to offer a fresh and accessible approach to international law, providing students with a uniquely holistic understanding of the field. Starting with the legal principles that underpin each strand of international law, and putting this into a real-life context, this textbook builds an understanding of how the international legal system operates and where it is heading. It guides readers through the theoretical foundations and development of international law norms, while also explaining clearly how the law works in practice. Key Features: Further reading and discussion topics for each chapter A focus on legal theory and how it intersects with the practice of international law A new chapter providing an extensive and up-to-date explanation of the specialised areas of international law An integrated and contextual examination of the political and extra-legal dimensions of the international legal system The latest treaties, case studies and analysis, including critical current issues such as the COVID-19 pandemic and global health, and climate change Taking into account the burgeoning literature, cases and legislative developments in public international law in the decade since its first publication, this edition offers new tools to help students embed their understanding, as well as new material on specialised areas of international law. This book is the perfect companion for students to learn international law in context, and for practitioners who want a firm theoretical foundation on which to base their practice.