This article focuses on theoretical reflections on sovereignty and constitutionalism in the context of the globalization and Europeanisation of the nation states, their politics, and legal systems. Starting from a critical assessment of the Kelsen-Schmitt polemic, the author claims that sovereignty needs to be analysed by the sociological method in order to disclose its current structural differentiation. The constitution of society may be imagined as the multitude of self-constituted and functionally differentiated social subsystems. The constitutional pluralism argument subsequently reconceptualizes sovereignty as socially differentiated and divided between specific subsystems. The EU's differentiated constitutional domain and the paradox of divided sovereignty are used as examples of profound structural and semantic changes in contemporary national and transnational societies. While the sovereign nation-state institutions have become marginalized in political structures of European societies, the self-constitutionalization of the functionally differentiated EU legal system proceeds by internalizing the concept of divided sovereignty and using it semantically as its mode of self-reference.Although the notion of a "sovereign state" may obfuscate rather than clarify the current state of national and international law and politics, sovereignty remains the starting point of many legal, political and social theoretical arguments. It is considered a relational concept with both legal and political dimensions and often described as paradoxical: It is constitutive of politics but escapes the regulatory logic of political institutions and belongs to the domain of "real life" with all its excesses; in modern constitutional rule of law it is both defining and defined by positive law and thus both outside and inside the juridical domain; furthermore, it signifies both the power that enacts laws (the political sovereignty of pouvoir constituent) and the law that restrains and regulates the constituent power of the people (the legal sovereignty of pouvoir constitué) (see, for instance, Loughlin 2003; Loughlin and Walker 2007).Sovereignty, together with democracy and constitution, forms the conceptual trinity of legal, social, and political theory which creates the many different semantic linkages and complex reflections of modern political societies. It is one of the constitutive metaphors of modernity and its persuasive force still profoundly affects theoretical discussions of the last three decades, reflecting the social transformation of modernity into postmodernity with its recent conceptualizations of "post-sovereignty" (Mac-