The Court of Justice of the European Union has exclusive jurisdiction over European Union law and holds a broad interpretation of these powers. This, however, may come into conflict with the jurisdiction of other international courts and tribunals, especially in the context of so-called mixed agreements. While the CJEU considers these 'integral parts' of EU law, other international courts will also have jurisdiction in such cases. This book explores the conundrum of shared jurisdiction, analysing the international legal framework for the resolution of such conflicts, and provides a critical and comprehensive analysis of the CJEU's far-reaching jurisdiction, suggesting solutions to this dilemma. The book also addresses the special relationship between the CJEU and the European Court of Human Rights. The unique interaction between these two bodies raises fundamental substantive concerns about overlaps of jurisdiction and interpretation in the courts. Conflicts of interpretation manage largely to be avoided by frequent cross-referencing, which also allows for much cross-fertilization in the development of European human rights law. The link between these two courts is the subject of the final section of the book.