In a large body of case law, constitutional courts from the EU Member States have reviewed European law on their compatibility with national constitutional law. These EU-related judgments deal with issues of major constitutional importance such as the EU’s democratic legitimacy, the protection of persons’ fundamental rights and freedoms, and the division of competences between the EU and its Member States. Yet are constitutional courts the institutions that should decide such issues of major constitutional importance for the EU? Or is it more democratic to leave these matters to political institutions that represent Europe’s citizens and that are supposedly politically accountable to them? In the current literature, the national constitutional courts’ EU-related case law is often evaluated in a positive light: it can help ensure respect for the Member States’ constitutional identities, function as a check on the EU’s powers, open up a space for contestation and dialogue, or serve as a justified response to a perceived EU democratic deficit. By contrast this book argues that the courts impose constitutional limits on the EU in a way that is often difficult to justify democratically. The book builds on political philosophy and constitutional theory to better understand the democratic legitimacy of the constitutional courts’ role in the EU. Through in-depth case studies of the German Constitutional Court and its political impact, as well as a comparison with the Netherlands where such review is absent, the book details how the German Court risks debilitating political debate on the future of Europe.