Terra nullius

Terra nullius (/ˈtɛrə ˈnʌliəs/, plural terrae nullius) is a Latin expression meaning "nobody's land". Since the nineteenth century, it has occasionally been used in international law as a principle to justify claims that territory may be acquired by a state's occupation of it. There are currently three territories sometimes claimed to be terra nullius: Bir Tawil (a strip of land between Egypt and Sudan), four pockets of land near the Danube due to the Croatia–Serbia border dispute, and parts of Antarctica, principally Marie Byrd Land.

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 a 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.

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 Straumann, 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 de 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 terms."

Alberico Gentili, in his De Jure Belli Libri Tres (1598), drew a distinction between the legitimate occupation of land that was res nullius and illegitimate claims of sovereignty through discovery and occupation of land that was not res nullius, as in the case of the Spanish claim to the Americas. Hugo Grotius, writing in 1625, also stated that discovery does not give a right to sovereignty over inhabited land, "For discovery applies to those things which belong to no one."

By the eighteenth century, however, some writers argued that territorial rights over land could stem from the settlement and cultivation of that land. William Blackstone, in 1765, wrote, "Plantations or colonies, in distant countries, are either such where the lands are claimed by right of occupancy only, by finding them desert and uncultivated, and peopling them from the mother-country; or where, when already cultivated, they have been either gained by conquest, or ceded to us by treaties. And both these rights are founded upon the law of nature, or at least upon that of nations."

Several years before Blackstone, Emer de Vattel, in his Le droit des gents (1758), drew a distinction between land that was effectively occupied and cultivated, and the unsettled and uncultivated land of nomads which was open to colonisation.