The challenge of thinking about the place of constitutionalism beyond the conventional categories of the nation state has become a principal concern for legal and political scholars. This book casts this issue in a different light by exploring the implications for the constitutionalism of legal integration in the European Union's 'area of freedom, security and justice'. In doing so it makes a novel contribution to an understanding of the European Union as a political community beyond the state, but in addition explores how this entails thinking differently about what is essential concerning constitutionalism. The book argues that instead of seeking to theorise constitutional foundations we actually begin to encounter the constitutional life implied by political and legal practices in the European Union and as exemplified here by 'the area of freedom, security and justice'.