Critical Border Studies emphasise how distinct political spaces are produced by borders. In this article I suggest that the order of this relationship should be reversed. I argue that space precedes and conditions the manifestation of borders. The argument is based on an understanding of cartography as a practice that mediates the relationship between space and borders. Drawing on Bruno Latour, I introduce the notion of cartopolitics to describe the process where questions pertaining to sovereign control over space are decided through cartography and law. In analysing current border practices in the Arctic, the term cartopolitics captures how the relationship between the United Nations Convention on the Law of the Sea and cartography is shaping the attempts by Arctic states to expand sovereign rights into the sea. The key is the continental shelf and how it is defined in law. In this process cartographic practices work to establish a particular spatial reality that subsequently serve as a basis for border making.