Abstract The judgments of the European Court of Justice (ECJ) of December 2008 in Viking and Laval on the compatibility of national collective labour law with European prerogatives have caused quite a heated critical debate. This article seeks to put this debate in constitutional perspectives. In its first part, it reconstructs in legal categories what Fritz W. Scharpf has characterised as a decoupling of economic integration from the various welfare traditions of the Member States. European constitutionalism, it is submitted, is bound to respond to this problematique. The second part develops a perspective within which such a response can be found. That perspective is a supranational European conflict of laws which seeks to realise what the draft Constitutional Treaty had called the motto of the union: unitas in pluralitate. Within that framework, the third part analyses two seemingly contradictory trends, namely, first, albeit very briefly, the turn to soft modes of governance in the realm of social policy and then, in much greater detail, the ECJ's hard interpretations of the supremacy of European freedoms and its strict interpretation of pertinent secondary legislation. The conflict-of-laws approach would suggest a greater respect for national autonomy, in particular, in view of the limited EU competences in the field of labour law.