terra nullius

Legal-invader-mumbojumbo which states that the land being invaded has no current owners, thus negating the need for invaders to officially declare war on the indigenous people of the land.

Cause of lots of headaches in Australia particularly, with it being declared illegal by the High Court thanks to the work of Eddie Mabo.

As one might expect, terra nullius translates into precisely "Land of no one", or, "No man's land".