This chapter examines recent conceptualisations of EU constitutionalism and the concepts of power, authority and legitimacy in the post-national EU pluralistic political and societal constellation. Constitutional pluralism of the EU needs to be comprehended not merely as a jurisprudential problem of the two or more legal systems operating within the EU and mutually recognising each other's normative claims, but as a sociological problem of the plurality of social systems, subsystems, knowledge and normative regimes constituting the European society by their differentiated self-constitutions. Self-limitation of the European legal system and its recognition of normative and societal pluralism is important because, apart from the imaginary of constitutional pluralism itself, it also reveals other imaginaries evolving beyond EU legality such as the imaginary of calculemus legitimising the system of EU administration and its capacity of social steering, the imaginary of imperium of prosperity generated by and evolving through the common market and its economic constitution, and the imaginary of politically mobilised democratic communities responding to the political consequences and crises of European integration beyond the imaginaries and institutions of the nation state.