(in international law) A method of acquiring territory in which good title can be gained by claiming previously unclaimed land (terra nullius). In the early days of European exploration it was held that the discovery of a previously unknown land conferred absolute title to it upon the state by whose agents the discovery was made. However, it has now long been established that the bare fact of discovery is an insufficient ground of proprietary right.
The distinction between acquisition by cession and acquisition by discovery was based upon the difference between organized and unorganized societies. The North Island of New Zealand, for example, was treated as a case of acquisition by cession; whereas the South Island, which was largely uninhabited and not generally under the rule of any chiefs, was treated as a case of discovery. Equally, since the discoverers believed that the Australian aborigines were incapable of intelligent transactions with respect to land, Australia was treated as a terra nullius.