This paper will be reflecting on Kant’s distinction between “forms of sovereignty (forma imperii)” and “forms of government (forma regiminis)” (PP 352; MM 6:340-1). Kant introduces this distinction in the context of referring to the different forms of states, and his main motivation seems to be to make the point that the question concerning the manner the political authority is exercised is more important than the question of who holds the supreme political authority in a state. I will argue that this distinction is particularly interesting for several reasons. First, it entails Kant’s ideas concerning the nature and significance of the principle of sovereignty in a political-legal union. Second, this distinction is pivotal for his ideas concerning political change. Third, it is a key to understanding the distinctive form of republicanism (i.e. liberal republicanism) Kant adheres to. In the end, I will discuss whether Kant’s distinction is defensible indeed.