Hundreds of immigration detainees could be released depending on a High Court judgment being handed down in a watershed legal challenge brought by an Iranian asylum seeker.
The detained 37-year-old man, known as ASF17, has taken his legal bid for freedom to the High Court arguing he should not be deported to Iran.
Australian authorities have attempted to deport him to the conservative nation every six months since 2018, when his asylum-seeker visa was refused.
The High Court previously ruled indefinite detention with no prospect of deportation is unlawful. (Lukas Coch/AAP PHOTOS)
As a bisexual man, ASF17 could face the death penalty upon return.
His case springs from a landmark High Court ruling in November, which found it was unlawful and unconstitutional to indefinitely detain people with no prospect of deportation.
About 150 immigration detainees were released as a result.
He told authorities they could deport him anywhere else, but Australia has not offered other options, so he remains in detention.
ASF17 first sought asylum to Australia by boat in 2013 and has been in detention for a decade.
The High Court is due to deliver its judgment on Friday morning.
Home Affairs Minister Clare O'Neil said the government had argued he should remain in detention and the government should retain its power to detain people in similar circumstances.
Ahead of the court 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 the coalition, the Greens and the crossbench forcing into to a senate inquiry.
The same unlikely trio again held up the bill providing three dissenting reports to the government's controversial bill on Monday sending it back to the senate for a vote.
The bill has been slammed as flawed and unjust by dozens of human rights and diaspora groups as well as the cross-party parliamentary human rights committee.