The idea of European union is as old as the European idea of the sovereign State. Yet the spectacular rise of the latter overshadowed the idea of a European Union for centuries. Within the twentieth century, two ruinous world wars and the social forces of globalization have however increasingly discredited the idea of the sovereign State. The decline of the – isolationist – State found expression in the spread of inter-state cooperation. The various efforts at European cooperation after the Second World War formed part of that transition from an international law of coexistence to an international law of cooperation. Yet European “integration” would go far beyond the traditional forms of international “cooperation”.

The European Union was born in 1952 with the coming into being of the European Coal and Steel Community (ECSC). Its original members were six European States: Belgium, France, Germany, Italy, Luxembourg, and the Netherlands. The Community had been created to integrate one industrial sector; and the very concept of integration indicated the wish of the contracting States “to break with the ordinary forms of international treaties and organizations”. The 1957 Treaties of Rome created two additional Communities: the European Atomic Energy Community and the European (Economic) Community. The “three Communities” were partly “merged” in 1967, but continued to exist in relative independence. A first major treaty reform was effected in 1987 through the Single European Act, but an even bigger organizational leap was taken by the 1992 Maastricht Treaty. The latter integrated the three Communities into the (Maastricht) European Union.

But for a decade, this European Union was under constant constitutional construction (Table 0.1). Treaty amendment followed treaty amendment! And in an attempt to get away from the ever-repeating minor treaty amendments, a European Convention was charged to prepare a major reform that would result in the “Constitutional Treaty”. The 2004 Constitutional Treaty would have effected the biggest structural change in the history of the European Union. Yet the Treaty failed when Dutch and French referenda were lost; and it took almost another decade to rescue the reform effort into the 2007 Reform (Lisbon) Treaty.