A decision next week on whether correct procedure was followed in the removal of former Papua New Guinea prime minister Sir Michael Somare from his East Sepik regional seat could also affect the legality of the Peter O'Neill government.
Mr O'Neill's administration was established in early August after a controversial parliamentary vote declaring the prime minister's position vacant with Sir Michael in Singapore for medical care.
He is challenging this in the Supreme Court.
Additionally Sir Michael wants the courts to declare null and void his removal as East Sepik member last week on the grounds he'd missed three consecutive sessions without approval.
Our correspondent, Oseah Philemon, says the outcome of this case, due just before parliament resumes on Tuesday, is likely to have a lot of bearing on the Supreme Court decision.
"If [Sir Michael] Somare is reinstated and he attends that means he has not missed three consecutive sessions of parliament, that means there is no vacancy in the office of the prime minister, so that is going to have a very very big bearing on the decision of the Supreme Court."