This book offers a comprehensive examination of the Court of Justice of the European Union (CJEU) and its engagement with public international law. It explores how the Court has developed a flexible, context-dependent approach to international law, which seeks to balance the autonomy of the EU legal order with the necessity of recognising and integrating international legal principles. Rather than focusing on landmark cases, the book analyses the CJEU’s jurisprudence thematically, exploring the various ways the Court encounters and engages with international law. These include the use of international law as a source and inspiration of EU law, as a method of challenging the validity of EU law, and as method of interpretation. The book goes beyond analysis of the judgments and explores the broader context in which the Court navigates its relationship with international law. It examines the circumstances under which the Court establishes barriers around the EU legal order, such as when it develops the principle of autonomy, and when it builds bridges with the international legal order, such as when it seeks to engage with and develop international law principles. This book will be of interest to scholars, practitioners, and students focused on the intersections of EU law and public international law, contributing to ongoing debates about legal pluralism and the evolving dynamics of intersecting legal frameworks.