On October 29, 2004, the leaders of the governments of the European Union member states (or heads of state, such as the Presidents of France and Cyprus) signed in Rome the text of the "Treaty establishing a Constitution for Europe".

The term "Constitution" was of course used occasionally in the past in theory with its substantial meaning, to indicate the existence of a set of rules governing the formation and organization of power in the European Union and its Communities. Moreover, the Court of Justice of the European Communities (CJEU) referred to the founding treaty of the former European Economic Community (EEC) as the "constitutional charter of a society governed by law".

However, the official declaration of the existence of a "Constitution for Europe" and its identification with a specific written text has significant political and ideological importance.