Kelsen and Schmitt, two leading legal theorists of the twentieth century, constitute a powerful pair that sheds light on the intertwining of politics and law in the phenomenon of sovereignty. Although their conceptions of sovereignty are far apart, they are interconnected as different ways of making sense of the same social phenomenon, or what I call the ‘practice of sovereignty’, whereby an ultimately unauthorised authority continuously authorises itself as the authority and the rest by and large accept this, acquiesce in this, or are made to do so. Having clarified their differences and interconnection, I explore some of the implications of the two writers’ differing conceptions of sovereignty and of the practice of sovereignty that underlie them.