Two Aboriginal men who were held in immigration detention will ask the High Court to find that Aboriginal non-citizens cannot be deported, in a case one expert describes as “landmark”.

In submissions filed with Australia’s highest court last week, lawyers for Daniel Love and Brendan Thoms argue that the government cannot deport an Aboriginal person who is not a citizen but has at least one Australian parent, came to Australia as a young child and has only left the country for short periods.

The lawyers say people with these characteristics cannot be considered “aliens” under the Australian Constitution.

Love, 39, was born in Papua New Guinea to an Aboriginal Australian father and a Papua New Guinean mother. He moved to Australia at age five, and has only left once since then.

In 2018 a delegate of home affairs minister Peter Dutton cancelled Love’s permanent visa after he was charged with assault and sentenced to 12 months imprisonment. He spent seven weeks in immigration detention until a delegate reinstated his visa.

Thoms, 31, has been in immigration detention since Sept. 2018. He was born in New Zealand to an Australian mother and New Zealander father. Since moving to Australia at age six, he has gone overseas twice but not since he was 14. He was sent to prison and his visa was cancelled for a domestic violence assault.

Both identify, and are recognised, as Aboriginal: Love is a member of the Kamilaroi people, and Thoms is a member of the Gunggari people and also holds native title. Both are also fathers to Australian children.

The case will be a “landmark decision”, Sangeetha Pillai, a constitutional law academic and expert in Australian citizenship law, told BuzzFeed News.

“You’ve got two Aboriginal people who have lived in Australia the overwhelming majority of their lives but were born overseas and [so] don’t hold Australian citizenship,” Pillai said. “So the question the High Court has been asked to rule on is whether a person in that position is a member of the constitutional community in Australia despite not holding statutory citizenship.”

Harry Hobbs, an expert in public law and Indigenous rights at the University of Technology Sydney, agreed that the case could be “significant”.

If the court ruled in favour of Love and Thoms, “it would reflect (and continue) a profound shift in state approaches towards Aboriginal people,” Hobbs told BuzzFeed News. He said the constitution initially excluded Indigenous people from the political community in a number of ways. A victory for Love and Thoms “would recognise that Aboriginal people cannot be regarded as not belonging to and within the community,” he said.

It would come nearly 30 years after the High Court recognised in the Mabo case that Aboriginal people have special land rights stemming from their traditional laws and customs.