Terra Nullis should be used in its correct context.  It was never used as a term by Captain Cook or Governor Phillip. 

Territorium nullis was first used in a meeting of the Institut de Droit International in 1888 regarding

Indeed it is a term that entered common use in the mid nineteenth century and is latin and the direct translation interpretation means “nobody’s land”.  Terra Nullis has been assailed by current day activists as means of invalidating the basis of Australian sovereignty.

It is clearly stated and acknowledged [through records] by Captain Cook and Governonr Phillip and settlers that there were Aboriginal people present since first sightings in 1770. 

There is no record stating that neither Captain Cook or any of the early governors of the Colonies ever referred to the land as terra nullis or nobody’s land.

Captain Cook was the first European to discover the East Coast of Australia and then proceeded to map the East Coast and then claim the land for King George III at  Possession Island in 1770.

The act of claiming land was common amongst the Colonial Empires.  The Without effective occupation following the claim

Priivy Council 1889

The English common law of the time allowed for a legal settlement of “uninhabited or barbarous country”  The presence of scattered and nomadic Aboriginal groups was evidence of a barbarous country  with no centre of government, without the means to defend itself, without any evidence of permanent residence or civilisation.

 

That fallacy lasted well into the twentieth century, the High Court writing in 1979 that Aboriginal peoples "have no legislative, executive, or judicial organs by which sovereignty might be exercised…The contention that there is in Australia an aboriginal nation exercising sovereignty, even of a limited kind, is quite impossible in law to maintain" (qtd. in Reynolds 95).

It might be presumed that the native inhabitants of any land have an incontrovertible right to their own soil: a plain and sacred right, however, which seems not to have been understood. Europeans have entered their borders uninvited, and, when there, have not only acted as if they were undoubted lords of the soil, but have punished the natives as aggressors if they have evinced a disposition to live in their own country. (qtd in Crowley 526).