PNG Opposition Leader Belden Namah is behind a summons filed with the national court which seeks to stop the PNG government from detaining people on the island.
Part of the summons seeks a declaration that PNG's Migration Act only applies to people seeking refuge in PNG, not those seeking refuge in other countries such as Australia.
The constitutionality of the memorandum of understanding between the PNG and Australian governments on reopening the Manus Island detention facility has been questioned even since the agreement was struck in September.
The Australian government believes offshore immigration processing will help reduce the amount of illegal refugee-carrying boats arriving on its shores.
The MoU helped further strengthen diplomatic ties between the two neighbours, plus provide some business and work opportunities on Manus Island.
The summons by Namah's lawyers is available here.