Large-scale migration constitutes an unavoidable social reality within the European Union. A European polity is made possible and tangible by the individual acts of migrants crossing the internal borders, developing a transnational life and integrating into European societies. Consequently, migration has become a special feature of the self-understanding of the European Union: its existence depends upon a continuing flow of persons crossing the borders of the Member States, and also upon the management of the flows of third-country nationals knocking at its doors. To respond to this challenge, the Union has developed common European migration policies. This book is a collection of essays which aim to explore a selected number of issues related to the development of these policies. It presents the current state, and the future of European immigration law discussing the political rationales and legal competences driving the action of the Union in this area. It reflects on the cooperation of the Union with third countries and on the emergence of international migration legal norms. It illustrates the role of the European Courts and the emergence of new actors through the adoption of EU instruments.