How does the European Union affect devolution and nationalist conflict in member states? Does the EU reduce the scope of regional self-government or enhance it? Does it promote conflict or cooperation among territorial entities? These are pressing questions in Spanish politics, where devolution has been an important tool for managing nationalist disputes, and for the Basque Country, where protracted and sometimes violent nationalist conflicts persist. Addressing these issues, this book explores prospects for an autonomous Basque role in EU politics; institutional arrangements for autonomous community participation in EU decision making; Basque government alliances with other regions and the EU's supranational bodies; EU incentives for collaboration among Basque and central state authorities; the impact of EU decisions on politically sensitive Basque competencies; and the incidence of EU issues in nationalist disputes. It presents a new theoretical framework for analysing the impact of the EU on regional power and will be of interest to students, researchers and general observers of Basque, Spanish and EU politics.