In the following essay, I attempt to reactualize some of Kant’s most fundamental conceptions of a state’s sovereignty and the legitimacy of the cosmopolitan order. To this end, I provide what appears as a viable solution to Kant’s “sovereignty dilemma”; that is, the reconciliation between state sovereignty and the international enforceability of laws. I consider that a key component of the overall Kantian cosmopolitan project is the role played by the transcendental notion of an “originally united will” in its validation of constituencies. I emphasize the view that for Kant state-citizens are also, as he says, “citizens of the world” (Weltbürger) or “citizens of the earth” (Erdbürger). I argue, furthermore, that a state’s sovereignty must comply with a number of different constitutional wholes. I then proceed by confronting the Kantian notion of a general united will with the Habermasian conception of “double sovereignty.” I conclude by suggesting a fusion/synthesis between the two views, one which would require endorsing the idea of cosmopolitan constitutionalism as a meta-framework for interpreting the legitimacy of member states’ compliance with policy indications of transnational constituencies.