This chapter takes up the first, conceptual step to develop a successful theory of jurisdiction. Based on how jurisdiction is described in views analysed in Chapter 3, but also in the literature on extraterritorial obligations in the area of economic and social rights, it shows that jurisdiction is often described by reference to a concept of power. I also show that it is common for courts and commentators to use terms such as power, control, or influence interchangeably. Following on from these insights, the main argument of the chapter is that the concept of power is rightly placed at the core of jurisdiction. However, this is only true for a clearly defined concept of power best understood as an ability. Based on this understanding, I show that power should be distinguished from influence, (use of) force, and control, respectively. These distinctions allow us to capture the difference between power, its exercise, the means through which it is manifested, and the outcome of the exercise of a given power.