term terra nullius gradually replaced territorium nullius. Fitzmaurice argues that the two concepts were initially distinct, territorium nullius applying to territory in which the inhabitants might have property rights but had not developed political sovereignty whereas terra nullius referred to an absence of property. Nevertheless, terra nullius also implied an absence of sovereignty because sovereignty required property rights acquired through the exploitation of nature. Michael Connor, however, argues that territorium nullius and terra nullius were the same concept, meaning land without sovereignty, and that property rights and cultivation of land were not part of the concept. The term terra nullius was adopted by the International Court of Justice in its 1975 Western Sahara advisory opinion. The majority wrote, "'Occupation' being legally an original means of peaceably acquiring sovereignty over territory otherwise than by cession or succession, it was a cardinal condition of a valid 'occupation' that the territory should be terra nullius – a territory belonging to no-one – at the time of the act alleged to constitute the 'occupation'.” The court found that at the time of Spanish colonisation in 1884, the inhabitants of Western Sahara were nomadic but socially and politically organised in tribes and under chiefs competent to represent them. According to State practice of the time the territory therefore was not terra nullius. Current claims of terra nullius Currently, there are three territories claimed to be terra nullius, Marie Byrd Land in Antarctica, Bir Tawil in the border between Egypt and the Sudan, and several small areas along the Croatia–Serbia border. Antarctica While several countries have made claims to parts of Antarctica in the first half of the 20th century, the remainder, including most of Marie Byrd Land (the portion east from 150°W to 90°W), has not been claimed by any sovereign state. Signatories to the Antarctic Treaty of 1959 agreed not to make such claims, except the Soviet Union and the United States, who reserved the right to make a claim. Bir Tawil Bir Tawil is an example of a territory often claimed to be terra nullius. Between Egypt and the Sudan is the landlocked territory of Bir Tawil, which was created by a discrepancy between borders drawn in 1899 and 1902. One border placed Bir Tawil under the Sudan's control and the Halaib Triangle under Egypt's; the other border did the reverse. Each country asserts the border that would give it the much larger