The fate of hundreds of indefinitely detained immigrants hinges on a landmark legal challenge before the High Court.
Hearings will begin in Canberra on Wednesday into the case of a detained Iranian immigrant making a legal bid for freedom.
His case springs from an earlier High Court ruling, which found it was unlawful to indefinitely detain people with no prospect of deportation.
About 150 immigration detainees were released as a result.
The Iranian man, known as ASF17, wants this expanded to cover people who refuse to co-operate with authorities on their deportation.
The 37-year-old was detained after his bridging visa was cancelled in 2014.
His asylum application was rejected a few years later and the federal government has since been attempting to deport him.
But his sexuality puts him at risk of the death penalty if he returns to Iran.
He told authorities they could deport him anywhere else, but Australia has not offered other options, so he remains in detention.
There are about 200 other people in a similar situation, a number of whom are suspected to have had their protection claims refused under a visa "fast-track" process.
The scheme will be abolished on July 1 but the Human Rights Law Centre accused the government of failing to help those refused visas under it.
Sanmati Verma, a legal director at the law centre, said the government was using indefinite detention as a way to "coerce people into returning to danger".
"People in detention are deprived of their freedom, separated from their families and communities and routinely subjected to violence, isolation and deplorable conditions," she said
"Indefinite immigration detention can never be the answer."
The High Court case could impact another 4000 people.
Ahead of the hearing, the government tried to ram through laws to prevent a mass release of people from immigration detention.
Under the proposed laws, those who refuse to co-operate with the government over their deportation - which includes those on some bridging visas - could spend up to five years in prison.
The legislation would give the home affairs minister unilateral power to ban visa classes of relatives of asylum seekers who come from blacklisted countries that do not accept deportees.
But it was blocked by an unlikely union between the coalition, the Greens and the crossbench and sent to a senate inquiry.