Two Aboriginal men only known as "Dick" and "Jack" have been remembered at the place where they were hanged two hundred years ago, amid concerns they were unjustly found guilty of killing a settler.

A commemoration of the pair was held at Tasmania's Treasury Building in Hobart on Thursday, along with a call for the building to be verified as Aboriginal land.

That plea comes as the state government tries to pass a bill to transfer the land into Crown ownership so it can sell it off.

Nala Mansell of the Tasmania Aboriginal Centre said the building was heritage listed because of its colonial values but Aboriginal people also had heritage connections as it was where Dick and Jack were sentenced.

"Tasmania has got a pretty terrible history of not just ignoring the fact that Tasmania has an extensive ancient Aboriginal history, that even went so far as to claim that we didn't exist," she told AAP.

Ms Mansell said no one could point to any time when Aboriginal people in Tasmania ever relinquished the ownership of their lands.

"The colonial government never purchased it from us and never asked us for it."

Dick and Jack were sentenced at the Treasury Building in 1826 and hanged at the jail opposite.

Their trial was conducted before an all-white military jury and despite protests from members of the white community concerned they had been unjustly convicted, Governor George Arthur ordered their execution.

Former senator and Greens leader Bob Brown attended Thursday's commemoration and called for the Treasury Building property to be verified as Aboriginal land.

The land was never ceded by the Palawa people and was never given a Crown title by colonial governors after the British colony was set up in 1803, he said.

The Rockliff government wanted to sell the site and had a bill before state parliament to create the missing title to enable the sale, but that should be subject to a thorough inquiry, Mr Brown said.

"The land is very arguably still in the ownership of the First Tasmanians who are, at least, owed two centuries' rent,'' he said.

''The horrific fact that it is also the land on which two Aboriginal men were imprisoned and publicly hung, in a case of judicial murder in September 1826, makes the case for Aboriginal consideration in the land's future all the stronger."

Australian Associated Press