This work consists of interrelated essays by many past and present members of the European University Institute (EUI) Law Department. The contributors' essays address such issues as: the effects of integration upon certain national laws; the elaboration of EU law to provide a new framework for or replacement for national laws; the piecemeal development of specific legal strands of EU law and their intertwining with national or international laws; and the indirect and sometimes unintended consequences of European integration with regard to national, EU or international law.

What is meant when politicians and lawyers talk of an opt-out, of multi-speed Europe, of variable geometry and even of European Union a la carte? Will closer co-operation be authorized, and where? These and many other questions are addressed in this work, which deals with the intriguing and controversial development of increased differentiation in European Union law. Adopting a law in context approach, it offers an analysis of differentiation from the Treaty of Rome to the present, including the 1996 Intergovernmental Conference and the Treaty of Amsterdam, a categorization of differentiation...