The Vanuatu opposition is seeking a stay order through the Supreme Court on the government's deal with a Singaporean company, Vanuatu Trade Development Limited, to upgrade and run five airports and to build and operate a new international airport.
The concession agreement includes a Vanuatu government promissory note for 350 million US dollars, which would effectively underwrite the scheme.
The opposition has called the plan a scam.
It wants the courts to stop any parliamentary debate on the matter.
Parliament is holding an extra-ordinary session this week aimed at gaining its approval for the deal, signed in July by the prime minister, Moana Carcasses and his deputy, Edward Natapei.
Parliament would also need to approve the promissory note, but opposition MPs say they are yet to receive copies of the document.
The prime minister is proposing a parliamentary committee to revise the concession agreement.
But the opposition says with the government having a majority in parliament it will control the ad hoc committee.