A man is effectively stateless and remains in indefinite detention after Australia bungled his deportation to Papua New Guinea, the Federal Court has been told.
Gus Kuster has been in mandatory detention for two years after his Australian citizenship was revoked upon release from prison in 2018.
His lawyer Louise Goodchild told the court on Wednesday that Australia's immigration department would have known his PNG citizenship status was non-existent at the time of deportation.
"At the time (the minister) made the decision it was quite certain he was not a PNG citizen and we say having regard to that he was affectively stateless," she said.
The only alternative as it legally stands is "indefinite detention," she said.
The 42-year-old was born in Manus, PNG, and arrived in Australia aged three.
His Australian ties include his great grandfather fighting in Gallipoli and his grandfather fighting for the nation in World War 2.
Following jail time for drug and driving-related offences his citizenship was revoked and upon release from prison in 2018 he was placed in detention.
Kuster was removed "voluntarily" from Australia in 2019 and flew from Brisbane to Port Moresby, according to the facts before the court.
But he was denied entry and held on the plane as the PNG immigration authority could not find any record of him belonging there.
Shortly after he was flown back to Brisbane and has since remained in mandatory detention.
Ms Goodchild said Kuster was not afforded procedural fairness and submitted the natural justice process was also hampered when significant documents were deliberately withheld from her client.
An official wrote that he feared Kuster would complain if sent a letter about him between a senior diplomat and the Immigration and Citizenship Authority in PNG.
"That is extraordinary in circumstances where this is unequivocal correspondence regarding his position of PNG status," Ms Goodchild said.
"There was a positive decision made by the department not to provide significant evidence about his citizenship because of concerns he would use it to his advantage."
The court was told then-immigration minister Peter Dutton had asked to personally review the case.
The government's lawyer Ben McGlade submitted that at the time it was fair for the minister to find his citizenship status "uncertain".
He said departmental efforts in trying to liaise with PNG authorities "was like pulling teeth," and they had been sent confusing inaccuracies.
These included the misspelling of Kuster's name and his wrong date of birth.
"There was the possibility they had misconstrued the law," he said.
They also had not ruled out Kuster successfully applying for PNG citizenship status in the future.
