European integration is now seventy years old and is about to turn into a historical research project of its own. It rests on the premise that the nation states share a common heritage, as well as intellectual, economic, political and philosophical foundations which hold the European legal system together. Law and integration through law are the means to realize the ambitious project (Chapter 24). The European Court of Justice (ECJ) is regarded as the motor of integration. The European Single Act advocated the building of an internal market, no longer through the four market freedoms and competition law alone, but most prominently through secondary EU law.