The European Union (EU) is in a state of transformation with its constitutional future the subject of much heated debate. This book provides a durable, authoritative and comprehensive account of constitutional development, examining the pivotal roles of law and judicial politics in establishing the EU constitutional edifice. Michael Longo demonstrates and substantiates the arguments for and against constitutionalisation through the development of a theoretical framework drawing on theories and empirical research in both law and political science to understand this new process of European Integration.