In this paper, we examine the extent to which the concept of emergence can be applied to questions about the nature and moral justification of territorial borders. Although the term is used with many different senses in philosophy, the concept of “weak emergence”—advocated by, for example, Sawyer (2002, 2005) and Bedau (1997)—is especially applicable, since it forces a distinction between prediction and explanation that connects with several issues in the dis-cussion of territory. In particular, we argue, weak emergentism about borders allows us to distinguish between (a) using a theory of territory to say where a border should be drawn, and (b) looking at an existing border and saying whether or not it is justified (Miller, 2012; Nine, 2012; Stilz, 2011). Many authors conflate these two factors, or identify them by claiming that having one without the other is in some sense incoherent. But on our account—given the concept of emergence—one might unproblematically be able to have (b) without (a); at the very least, the distinction between these two issues is much more significant than has often been recognised, and more importantly gives us some reason to prefer “statist” as opposed to “cultural” theories of territorial borders. We conclude with some further reflections on related matters concerning, firstly, the apparent causal powers of borders, and secondly, the different ways in which borders are physically implemented (e.g., land vs. water).