Australia's new refugee medical evacuation process could be thwarted under new laws enacted by the Nauruan Government.

Key points: Medical transfers off Nauru must be approved by a new committee and the Health Minister

Medical transfers off Nauru must be approved by a new committee and the Health Minister The regulation was introduced within 72 hours of the Australian medical transfer bill passing

The regulation was introduced within 72 hours of the Australian medical transfer bill passing Refugee supporters fear people are now "held prisoner" on Nauru

The small nation's cabinet approved a change forcing all overseas medical transfers to be approved by a new committee and the country's Health Minister.

The rule explicitly bans transfers where the patient seeks assessment from an overseas-based doctor during the process.

"Individuals who urgently need a medical transfer to Australia from Nauru are now being held prisoner," lawyer George Newhouse said.

"This is a very crude attempt to stymie the legislation that came out of the Australian Parliament last week."

The crackdown was introduced within 72 hours of the Australian Parliament passing a bill to help refugees or asylum seekers travel to Australia for health care.

Under the new Australian law — which is yet to come into force — two doctors must assess the person on Nauru or Manus Island as needing further medical treatment or assessment.

The Opposition and Lower House crossbenchers defeated the Coalition in the first legislative loss for a government in decades.

Nauru's restrictions raise the prospect of a stand-off between the Australian Parliament and the small Pacific nation.

"It's not quite clear what they've done and how that will play out," Prime Minister Scott Morrison told 3AW.

"I'm still getting reports in of exactly what they've decided to do and what the legal force of that is."

It is unclear whether those assessed as needing a transfer outside Nauru would be transferred to Australia or elsewhere.

"The committee in making an overseas medical referral may prescribe the type and purpose of referral," the regulation states.

Under the rules:

All transfers from Nauru for treatment must go through its own Overseas Medical Referrals Compliance Committee

All transfers from Nauru for treatment must go through its own Overseas Medical Referrals Compliance Committee A Nauru-based health provider must believe "additional expertise or differently resourced facility are required"

A Nauru-based health provider must believe "additional expertise or differently resourced facility are required" Referrals are blocked if they follow "the recommendation of an overseas health practitioner [using] telemedicine examination or diagnosis"

The Australian Government confirmed refugees and asylum seekers transferred to Australia would be sent to Christmas Island unless they needed higher-level care.

"We'll have a look at the individual cases, but that's the default position," Home Affairs Minister Peter Dutton said.

"There's obviously a lot of effort that's underway at the moment to provide additional medical services on Christmas Island.

"Depending on the condition … judgements will be made about whether that person can be treated [on Christmas Island]."

Mr Dutton said detention centres in Australia were nearing capacity following the closure of facilities over recent years.

Greens immigration spokesman Nick McKim accused the Government of "subverting the intent of the Parliament".

He said supporters of the so-called Phelps bill wanted people brought to the mainland.

"Surely now it's time for some of the crossbenchers in the House of Representatives to reconsider their commitment of confidence in this Government," he said.

But Labor leader Bill Shorten played the issue down.

"If the medical treatment is required and it's delivered on Christmas Island and it makes people well, well that's fine," he said.

The ABC sought a response from the country's Australian-based media relations company, Mercer PR.

It referred questions to the Nauruan Government, which then referred queries back to the PR firm.