This is the first book to jointly scrutinise two existential issues for the EU: withdrawal of a member state (i.e. Brexit) and territorial secession (affecting Scotland, Catalonia and beyond). The book applies normative and empirical analyses, explores new approaches and discusses the deep theoretical problems unleashed by these processes. Featuring a superb constellation of legal and political science scholars, the book combines specific legal analysis and considers the political dynamics behind the processes. It provides extensive coverage and sophisticated analysis of the interpretation of Article 50 and the possible consequences it may have. The implications of withdrawal and secession on EU citizenship are discussed in depth and there is an overview of the evolving nature of the relationship between the regions and the EU. Finally, there is an engaging normative discussion on the deeper meaning of these two processes with respect to the objective of European integration.