European integration has created a constitutional asymmetry between policies promoting market efficiencies and policies promoting social protection and equality. National welfare states are legally and economically constrained by European rules of economic integration, liberalization and competition law, whereas efforts to adopt European social policies are politically impeded by the diversity of national welfare states, differing not only in levels of economic development and hence in their ability to pay for social transfers and services but, even more significantly, in their normative aspirations and institutional structures. In response, the ‘open method of coordination’ is now being applied in the social–policy field. It leaves effective policy choices at the national level, but tries to improve these through promoting common objectives and common indicators, and through comparative evaluations of national policy performance. These efforts are useful but cannot overcome the constitutional asymmetry. Hence there is reason to search for solutions which must have the character of European law in order to establish constitutional parity with the rules of European economic integration, but which also must be sufficiently differentiated to accommodate the existing diversity of national welfare regimes. The article discusses two such options, ‘closer co–operation’ and a combination of differentiated ‘framework directives’ with the open method of co–ordination.