Several years after the first Greek bailout, the integration project of the European Union faces an interlocking set of political, economic, legal and social challenges that go to the very core of its existence. Austerity is the order of the day, and citizens in both debtor and creditor states increasingly turn to the political movements of the far left and right, anti-politics and street protests to vent their frustration. This book demonstrates the limits of constitutionalism in the EU. It explores the `twin crises' - the failure of the Constitutional Treaty in 2005 and the more recent Eurozone crisis - to illuminate both the possibilities and pitfalls of the integration project. It argues that European integration overburdened law in an attempt to overcome deep-seated political deficiencies. It further contends that the EU shifted from an unsuccessful attempt at democratisation via politicisation (the Constitutional Treaty), to an unintended politicisation without democratisation (the Eurozone crisis) only a few years later. The book makes the case that this course is unsustainable and threatens the goal of European unity. This text will be of key interest to students and scholars in the fields of EU studies, EU law, democracy studies, constitutional studies and international relations.