A High Court case to decide the fate of a New Zealand man who claims Aboriginal identity by way of adoption could "shake the bedrock of what it means to be an Aboriginal person", Indigenous leaders say.
The federal government will use a hearing in Canberra today to challenge an earlier High Court ruling which found Aboriginal people could not be considered aliens under the constitution.
The ruling effectively put Aboriginal and Torres Strait Islander people beyond the reach of immigration laws, even if they were born overseas and didn't have Australian citizenship.
It meant Indigenous people in this category who had served time in jail and been deemed to have failed the character test could not be deported.
Yugambeh traditional owner and linguist Shaun Davies said the decision was as groundbreaking as the famous Mabo judgement in terms of Indigenous rights.
"It was a case that recognised that Aboriginal Australians are not aliens, we have a special connection to this country," Mr Davies said.
Mr Davies said to challenge the ruling would be a step backwards for Australia.
"It's just gobsmacking to think that we could come so far in Aboriginal politics and have a government that's working against us," he said.
"They are shaking the bedrock of what it means to be an Aboriginal person."
If the decision is overturned, it will leave some Indigenous non-citizens vulnerable to deportation.
"Just the very thought of that makes me want to cry," Mr Davies said.
"We're talking about a path to treaty and sovereignty and moving forward as Aboriginal people, but by the looks of it we're about to leave half the mob behind."
Aboriginal adoption in question
The main focus of the appeal is the case of Shayne Montgomery. He was freed from immigration detention after the Federal Court found his adoption by the Mununjali people meant he was covered by the High Court ruling.
He is a member of the same native title group as Mr Davies.
Mr Montgomery came to Australia in 1997, aged 15, the son of an Australian mother and New Zealand Māori father.
After a brief period of homelessness, he was taken in by members of the Mununjali Aboriginal community in Brisbane and was initiated and given a totem.
He now has five Australian children.
In 2018, Mr Montgomery was sentenced to 14 months' jail for aggravated burglary.
His lawyers said it was only in prison that Mr Montgomery realised he was not an Australian citizen.
An Immigration officer cancelled his visa and, after Mr Montgomery served his time in jail, he was taken into immigration detention.
But in November last year, the Federal Court found Mr Montgomery had been illegally detained.
He was released into the community in Western Australia.
The government is now appealing against the Federal Court's decision, arguing it was right to detain Mr Montgomery on the belief he was not Aboriginal.
Lawyers for the Commonwealth will tell the High Court that Mr Montgomery fails to meet a three-part test to prove his Aboriginality because he cannot demonstrate biological descent.
The test was established in the Mabo decision and includes that a person identifies as Indigenous, is recognised by other Indigenous people and has a biological descent.
While the government does not deny that Mr Montgomery identifies as Mununjali and is accepted by the group, it argues his adoption is not enough to claim Indigeneity.
'He wants to care for his kids'
The case has upset members of Mr Montgomery's clan group.
Mununjali elder Janis Page said adoption was a central part of her culture.
"If someone's been raised in a family, as a family … and they've adopted them as their own, well, then he becomes part of that culture," Ms Page said.
"If he's been raised on country, he's hunted on country, if he's been taught the ways on country, then he is Mununjali."
Mr Montgomery's lawyer, Arti Chetty, said it had been a stressful time for her client and his family.
She said if Mr Montgomery was deported to New Zealand, he would not be able to fulfil his obligations as a father and a knowledge holder within his community.
"It's been incredibly distressing for Shane," Ms Chetty said.
"It's really very simple for him. He wants to care for his kids. He wants to protect them. He wants to be with them."
Mr Montgomery's lawyers argue the government has misstated the case, and the High Court should confine itself to considering the legality of his detention.
They will tell the court his detention was illegal because the immigration officer who cancelled his visa lacked the "reasonable suspicion" he was an unlawful non-citizen.
In submissions to the court, Mr Montgomery's lawyers say the officer looked only at evidence from Mr Montgomery and his mother, and did not look at evidence from elders, other family members and an expert anthropologist.
Part of Mr Montgomery's evidence is that government agencies, including Centrelink, had recognised him as Aboriginal for a long period.
Government wants ruling overturned
While the government's primary focus is to show Mr Montgomery is not covered by the so-called Love and Thoms ruling, its lawyers will today use the opportunity to ask the High Court to consider throwing out that decision.
Submissions to the court have taken specific aim at the use of the Mabo definitions to determine whether a person is Indigenous.
They say there is a "misalignment" in using the Mabo test because it was set up for specific spiritual and cultural claims on land and sea, not for proving a more general link with Aboriginal society.
Mr Montgomery's lawyers say the court should not entertain the call to throw out the original ruling at this stage.
"Mr Montgomery's successful reinstatement of his liberty is the wrong vehicle to explore the Appellants' core objectives of having Love overturned or limited," the submissions to the court said.
New judges could sway outcome
The High Court was deeply divided over the original ruling, which was carried in a 4-3 majority.
The judges arrived at the same point, but differed in their reasons.
The Commonwealth will point to those differences today to support its argument that the ruling should be revisited.
Since the original judgement, two judges who ruled in favour of the "aliens" decision, Virginia Bell and Geoffrey Nettle, have left the bench.
This means if the decision is reviewed and even one of the two new judges, Simon Steward or Jacqueline Gleeson, goes the opposite way, the ruling could be overturned.
Mr Montgomery's lawyers have asked the court to order the Commonwealth to pay the costs, because it set it up as a test case.
At the end of last year, 21 people in immigration detention were being assessed as to whether they were Indigenous, according to the three-step test.
One of the men in the original case, Brendan Thoms, is now trying to sue the Commonwealth for nearly 500 days in immigration detention.
The High Court is still pondering a decision on whether his detention was legal.
