Papua New Guinea's opposition leader, Belden Namah, says Australia's Manus detention centre and asylum seekers scheme is unconstitutional.
Mr Namah says he is seeking a Supreme Court interpretation to get clarification on the detainees' visas, because foreigners can only get visas for tourism, employment or business.
He has also asked the government to explain how detainees can be held when they have not entered PNG illegally on their own accord or committed any crime there.
The prime minister, Peter O'Neill, says activities associated with the Manus asylum detention and processing centre are within the perimeters of PNG laws.
Australia reopened its Manus detention centre last year after closing it in 2004.