The Draft European Constitution was arguably both an attempt to constitutionalise the Union, re-framing that project in the language of the state, and an attempt to stretch the boundaries of constitutionalism itself, re-imagining that concept to accommodate the sui generis European Union. The (partial) failure of this project is the subject of this collection of essays. The collection brings together leading EU constitutional scholars to consider, with the benefit of hindsight, the purportedly constitutional character of the proposed Constitutional Treaty, the reasons for its rejection by voters in France and the Netherlands, the ongoing implications of this episode for the European project, and the lessons it teaches us about what constitutionalism really means.