It is clear that the current crisis of the EU is not confined to the Eurozone and the EMU, evidenced in its inability to ensure the compliance of Member States to follow the principles and values underlying the integration project in Europe (including the protection of democracy, the Rule of Law, and human rights). This defiance has affected the Union profoundly, and this book dissects the essence of this crisis, examining its history and offering coping methods for the years to come. Defiance is not a new concept and this volume explores the richness of EU-level and national-level examples of historical defiance—the French Empty Chair policy, the Luxembourg compromise, and the FPÖ crisis in Austria—and draws on the experience of the US legal system and that of the integration projects on other continents. Building on this legal-political context, the book focuses on the assessment of the adequacy of the enforcement mechanisms whilst learning from EU integration history. Structured in four parts, the volume studies theoretical issues on defiance in the context of multi-layered legal orders, EU mechanisms of acquis and values’ enforcement, comparative perspective on law-enforcement in multi-layered legal systems, and case-studies of defiance in the EU.