European constitutionalism is traditionally described as a limited model, oriented towards the commercial and economic objectives of the internal market and controlled under the principle of conferral. In reality, a more complex system of multilevel governance has emerged in recent years, which complicates the constitutional interpretation of the EU but may help explain the novelties and, above all, the difficulties of the evolution of the European integration process. This article uses the instruments of constitutional economics, particularly those intended to explain the mechanisms of constitutional change, to establish whether the introduction of new instruments of soft law could be considered useful in overcoming the «constitutional limits» of widening the integration process.