Terra nullius

international law term meaning territory which has never been the subject of a sovereign nation

Terra nullius means unclaimed territory. It is the correct term in international law. It means land which does not (at present) belong to any state. The term comes from the Latin, meaning Nobody's thing. There is also an expression no man's land, but that does not have a formal legal meaning.

The Croatia–Serbia border dispute in the Bačka and Baranja area. The Croatian claim corresponds to the red line, while the Serbian claim corresponds to the course of the Danube.
  Under Serbian control, claimed by Croatia
  Under de facto Croatian control, although not claimed by either Croatia or Serbia
Territorial claims in Antarctica. The area in white is unclaimed territory, or terra nullius

Rule over terra nullius can be got by occupying the territory.[1] There are various legal problems about this concept, but in practice it is often the business of neighbouring states to decide by negotiation. Diplomacy may sometimes be replaced by warfare.

Two territories that are currently terra nullius are Bir Tawil between Egypt and Sudan, and Marie Byrd Land, in Antarctica.

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