High Court to hear Nauru detention centre challenge

The legality of Australia's role in the Nauru immigration detention centre is set to be examined by the High Court.

The hearing before the full bench on Wednesday comes two days after the Nauru government made the centre an open facility and vowed to finalise all 600 outstanding refugee claims this week.

The test case focuses on the plight of a pregnant Bangladeshi asylum seeker brought to Australia from Nauru because of serious health complications.

She is now facing imminent return to the Pacific island with her 10-month-old baby.

The Melbourne-based Human Rights Law Centre is also running more than 200 other cases on similar legal principles.

"Australia should not be indefinitely warehousing people on remote islands, especially babies," said spokesman Daniel Webb.

The family was terrified of being forced back to an unsafe environment, he said.

The plaintiff's lawyers will argue there is no law that gives the federal government power to fund offshore detention centre arrangements.

The government responded by hastily passing retrospective legislation, Mr Webb said.

The High Court's ruling could also have legal implications for the other offshore detention centre on Manus Island, Papua New Guinea.

Lawyers for the Commonwealth say the plaintiff's case could not form the basis of a damages claim because that would fall under Nauruan law.

They will also argue that it is clearly within the non-statutory executive power of the Commonwealth to enter into a memorandum of understanding with the Nauru government.

The hearing is scheduled to go for two days.