Terra nullius (, plural terrae nullius) is a Latin expression meaning "nobody's land". It was a principle sometimes used in international law to justify claims that territory may be acquired by a state's occupation of it. There are currently three territories claimed to be terra nullius, two of which are caused by border disputes between sovereign states. Doctrine In international law, terra nullius is territory which belongs to no state. Sovereignty over territory which is terra nullius can be acquired by any state by occupation. According to Oppenheim: "The only territory which can be the object of occupation is that which does not already belong to another state, whether it is uninhabited, or inhabited by persons whose community is not considered to be a state; for individuals may live on as territory without forming themselves into a state proper exercising sovereignty over such territory." Occupation of terra nullius is one of several ways in which a state can acquire territory under international law. The other means of acquiring territory are conquest, cession by agreement, accretion through the operations of nature, and prescription through the continuous exercise of sovereignty. History Although the term terra nullius was not used in international law before the late nineteenth century, some writers have traced the concept to the Roman law term res nullius, meaning nobody's thing. In Roman law, things that were res nullius, such as wild animals (ferae bestiae), lost slaves and abandoned buildings could be taken as property by anyone by seizure. Benton and Strauman, however, state that the derivation of terra nullius from res nullius is "by analogy" only. Sixteenth century writings on res nullius were in the context of European colonisation in the New World and the doctrine of discovery. In 1535, Domingo de Soto argued that Spain had no right to the Americas because the lands had not been res nullius at the time of discovery. Francisco di Vitoria, in 1539, also used the res nullius analogy to argue that the indigenous populations of the Americas, although “barbarians”, had both sovereignty and private ownership over their lands, and that the Spanish had gained no legal right to possession through mere discovery of these lands. Nevertheless, Vitoria stated that the Spanish possibly had a limited right to rule the indigenous Americans because the latter “are unsuited to setting up or administering a commonwealth both legitimate and ordered in human and civil