This book explores the complex and ever-changing relationship between the European Union and its member states. The recent surge in tension in this relationship has been prompted by the actions of some member state governments as they question fundamental EU values and principles and refuse to implement common decisions seemingly on the basis of narrowly defined national interests. Furthermore, Brexit forces the EU for the first time to face the prospect of a major member state preparing to leave the Union. Are these developments heralding the return of the nation-state, and if so, in what form? Is the national revival a lasting phenomenon that will affect the EU for a long time to come, or is it a transitory trend? This book takes an interdisciplinary approach to answer these questions. It brings together scholars from economics, law, and political science to provide insights into the multifaceted relations between the Union and its member states from different perspectives. All chapters are based on up-to-date research findings, succinct assessments of the current state of affairs and ongoing debates about the direction of European integration. The book concludes by offering policy recommendations at European and national levels.