This contribution is concerned with the law of European integration, or what has been termed ‘integration through law’ (Cappelletti et al. 1986). The use of law as a means of European integration is legendary. It has been studied intensively by political scientists and legal scholars, and more recently also by sociologists (Frerichs 2008). The role of economists is no less important, be it as analysts or protagonists of integration through law. This is most obvious in debates on Europe’s ‘economic constitution’, which is a key concept in ordoliberal thinking (Sauter 1998). Indeed, law has been central in ‘constituting’ the internal market, which rests on the free movement of goods, services, capital and persons across national boundary lines. The four fundamental freedoms enlarge the space for private action — in particular market transactions — which fall into the domain of private law. Market integration thus seems to imply integration of private law, and ‘integration through private law’ (Caruso 2006: 43) to increase the efficiency of the internal market. It is on these grounds that emerging European society has been depicted as a ‘private law society’ (Grundmann 2008).