The high court of Australia will this week examine a complicated question: can Aboriginal or Torres Strait Islanders be deported as aliens if they don’t hold Australian citizenship?

The federal government says yes.

But lawyers for two Indigenous men facing removal from the country, backed up by the Victorian state government, say there is another option: non-citizen non-alien.

The special case hearing on Thursday before the full bench will examine a series of propositions, which were unusually put forward by the high court itself, and which go beyond the contentious issue of deportations.

The Australian government contends it is an issue of binary definitions and that, because the men are not citizens, they are therefore aliens and the minister has the power to cancel their visas.

Parties have already invoked significant precedents, including the Mabo ruling and the original act of colonisation, in arguing their cases.

The plaintiffs, Daniel Love and Brendan Thoms, have accused the commonwealth of alarmism and say if the high court rules in their favour it would not open borders to anyone claiming Indigenous heritage, but simply prevent the government detaining and deporting bona fide First Nations people.

Love and Thoms face deportation after the home affairs minister, Peter Dutton, cancelled their Australian visas over criminal convictions. Both are Indigenous, but they were born overseas and did not apply for citizenship after moving to Australia.

Love is a Kamileroi man born in PNG to an Aboriginal father and Papua New Guinean mother. He moved to Australia at the age of five.

Thoms, who arrived in Australia in 1994, is a Gunggari man and native title holder, born in New Zealand to an Aboriginal mother and New Zealand father.

They are among thousands of people whose visas have been cancelled under the controversial character test provisions of the migration act, and among a subset whose cases have attracted attention because they have spent the vast majority of their lives in Australia.

The case was last heard on 8 May, with the high court reserving its decision. Last month it was revealed the court had asked parties to submit arguments “as to whether members of an Aboriginal society have such a strong claim to the protection of the Crown, that they may be said to owe permanent allegiance to the crown”.

The court put forward a series of propositions setting out the legal logic that could lead to the conclusion that people recognised as Aboriginal could not also be classed as aliens.

The government argues that the propositions would create a class of persons outside both the Citizenship Act and the Migration Act, impairing the administration of both.

“Their right to enter would depend not on their status (as citizens or non-citizens holding visas), but on the answers to factual questions involving an unspecified degree of biological connection and self and group identification,” it says.

It says the 1992 Mabo ruling recognised that “the acquisition of sovereignty” by the British gave every person born in Australia between settlement and the mid-1980s the status of a British subject or – later – an Australian citizen, regardless of whether they were Indigenous or not.

That meant there was no reason for any “unique obligation” to Indigenous people to develop.

It says if the high court found that Indigenous people owed permanent allegiance to the crown and so could never be considered “alien”, it would go against the purpose of the 1967 amendments, and could be perceived as placing Indigenous people in an “unequal position” by denying them the autonomy to pledge allegiance to a foreign power.

The commonwealth argues that Indigenous people born in Australia would “with few, if any, exceptions”, be citizens under the law.

Lawyers for Love and Thoms say a ruling in the plaintiffs’ favour would simply prevent the commonwealth from deporting or expelling Aboriginal people who pass the current “three part test” which is used in native title cases.

“The high court has to determine the answer to one question – whether an Aboriginal person can meet the definition of an alien for the purposes of section 51,” says their lawyer, Claire Gibbs.

“In our view it means Aboriginal Australians cannot be aliens because they have a unique position in this country as the original inhabitants.

“Just as they’re entitled to native title rights, that also should give rise to protection from deportation and to not be included in the definition of an alien.”

In its submission as an intervening party, the Victorian government wrote in support of Love and Thoms, saying that because they were Aboriginal members of an Aboriginal society, and “because of the recognised mutual and unique relationship” between those members and Australian land and waters, the two men were not aliens as defined by the constitution.

The Victorian government submitted it was “irrelevant” that they were born outside of Australia and held citizenship of other countries.

The submission accuses the commonwealth of addressing “irrelevant topics and concepts” in its argument. “It suffices to note that then equivalence expressed between lacking the statutory status of citizenship and, as a result, carrying the constitutional status of an alien is unprincipled and wrong.”

It also pushes back against the commonwealth’s arguments about settlement, saying they appear to assert that Indigenous Australians’ role of caring for the country for up to 80,000 years “was subsumed into the new status and the common law regarded Indigenous Australians as the same as every other person born in Australia”, when Mabo 2 showed this not to be the case.

It says Indigenous people who inhabited Australia before settlement became British subjects “because they were the Indigenous inhabitants”. It followed that Aboriginality was “the crucial and central characteristic” that made them British subjects and therefore non-aliens.

The case is the first time Aboriginality has been considered in testing the definition of an alien under Australia’s constitution, and Gibbs says the men’s case is challenging the commonwealth’s binary interpretation.

“Their position is that because our clients were born outside this country and do not hold citizenship they are aliens. So they haven’t really engaged about the outer limits of that test and ... the unique characteristics of Aboriginality,” she says.

“The ordinary definition of alien is someone belonging to another. We think on any commonsense measure, on any correct interpretation of the common law, that an Aboriginal person cannot meet that definition.”

The high court will hear the case on Thursday.