Papua New Guinea's opposition leader is challenging the legality of Australia's asylum seeker processing centre on Manus Island.
Lawyers acting for Belden Namah have filed a summons with the national court in Port Moresby.
It asks the court to permanently restrain the PNG government from detaining people at the centre.
Mr Namah's lawyer Loani Hinau says the agreement that established the centre authorises the deprivation of liberty.
"And so far as foreigners are concerned, those personal liberties can be restricted or restrained by the government of this country if the foreigners have entered this country unlawfully. The refugees they did not break any laws, the laws in fact, in the submission we are making, were breached by the government of this country."
The lawyer for PNG's opposition leader, Loani Hinau