International law makes a claim to universality; it is supposed to be the law that applies to the relations among all peoples. This chapter argues that international law, instead, serves as a mechanism of closure; it provides a restrictive articulation of the rules that define which actors have a capacity for international rights. The chapter offers a reading of two of the most influential figures in early international law, Grotius and Vattel, in terms of the closure thesis. It traces the principle mechanism of closure to a notion of property rights that invests the territorial state with the capacity for rights based on possession and ownership. It then details how the combination of property and natural rights as the basis for sovereignty would justify the equal treatment of some and the domination and exploitation of others. Rules of closure served to accelerate the formation of property monopolies, first in the form of colonial extraction and later in the form of market neoliberalization. The chapter considers the contemporary implications of the international-law-as-closure argument. At stake is whether universalism is understood as a project of homogenizing differences and protecting privileges, or of making space for pluralism and diversity.