The book focuses on the common visa policy as a case study on the constitutional structure of the European Union. After introducing the nature of visas, the book concentrates on the difficulties in forging a common visa policy at European level. Cooperation on visas has been characterized by a continuous reformulation of the framework for cooperation. The book describes cooperation before the Treaty on European Union adopted at Maastricht, under the Maastricht Treaty, and under the Treaty of Amsterdam. Furthermore, the book traces the essential characteristics of the common visa policy.