European integration rests on the successful application, development, and reformulation of law. This process makes it possible to overcome political resistance, stimulate European legislation, and even substitute political decisions. The circumstances surrounding its creation and changing political resistance from the Member States spoke against its success. Ferdinand Weber analyzes the origins, conditions, and development of the mechanisms that, taken together, carry a federal self-constitution inside the contractual framework. Its key lies in a specific understanding of the European treaties and its translation into methodological approaches and doctrinal constructs. At the center stands an early, jointly held-though differently articulated-constitutional imagination of key institutions and actors which lead to a material hierarchization of the treaty objectives in relation to other norms of the European treaties. Methodologically, this constitutional imagination translated into a claim to effectiveness that distinguishes Union law from international law: the specific effet utile of Union law, which has achieved the status of a guiding norm. It stands at the top of the derivational framework of subsequent Union law doctrines, which, after gaining autonomy as principles or norms in their own right, detach themselves from their reference to it. The author explores the origins and further development of this process through an analysis of the effet utile, the protection of fundamental rights, European citizenship, and the values of the Union, before considering offers of legitimacy and the European Court of Justice as an "alternative judiciary."