Abstract: My dissertation explores ways that engaging with the history of settler colonialism should matter to work in contemporary political philosophy. I begin by critiquing the state of the debate in the philosophy of immigration. The most popular arguments for open borders–the view that people should nearly always be able to live and travel wherever they wish– are parallel to arguments historically made to justify settler colonialism. Unless seriously qualified, these arguments have the counterintuitive consequence that most historical settler colonialism was justified; they also have dire consequences for the rights of indigenous peoples today. However, most of the popular arguments for immigration restrictions also fail to account for the rights of indigenous peoples. How, then, can we understand the principled basis of those rights? I offer my own justification of territorial rights and (some) border controls based on NeoRoman republicanism. This is the view that the purpose of political institutions is to protect people from domination, where domination is understood as subjection to the arbitrary will of another. There is a growing literature on the question of what (if anything) is wrong with colonialism apart from obvious wrongs that are often perpetrated by colonizers such as physical violence, enslavement, and the displacement of colonized people from their homes. I argue that colonialism is a wrong even in the absence of violence etc. because it involves domination in the sense just mentioned. Furthermore, I argue that rights to control territory and impose (some) restrictions on immigration are justified as a means of preventing domination by settlers. Philip Pettit, the most influential neo-Roman republican, has argued that a state is necessary to secure non-domination. This would seem to imply that my justification of territorial rights as a means of preventing domination does not apply to non-state societies. In response to this objection, I draw on defenses of non-state forms of governance in American Indian/First Nations philosophy as well as the actual history of non-state societies to rebut Pettit’s arguments: non-state societies can successfully protect their members from domination and have actually done so.