We don't have Manus roadmap yet: PM

The federal government has no immediate plan for its under-threat offshore immigration detention regime in Papua New Guinea.

For now it is getting advice on a PNG court decision that ruled the detention of asylum seekers on Manus Island was illegal.

Lawyers are warning the government could be sued for false imprisonment.

Prime Minister Malcolm Turnbull says the matter is for PNG initially, but the ruling was under consideration at home and Australia would support PNG in figuring out a solution.

"I can't provide a definitive road map from here, but today ... we're getting briefed on it," he told reporters in Brisbane on Wednesday.

Immigration Minister Peter Dutton insists the male detainees on Manus won't be settled in Australia, but they can return home or go to another country willing to accept them.

The government is in talks with other countries that could take processed refugees while making sure it doesn't send the wrong signal to people smugglers.

The Human Rights Commission says the court ruling decision could leave Australia open to breaching international law obligations.

But the ruling confirmed Australia's detention policies were increasingly out of step with international norms, president Gillian Triggs said.

Labor dismissed Mr Dutton's comments as delusional, saying it was absurd to suggest the decision had no impact on government policy.

"Mr Dutton's attempt to downplay the ruling raises serious concerns about his lack of a contingency plan in response to the ruling," opposition immigration spokesman Richard Marles said.

The Greens said neither party had a proper exit strategy and the unsustainable "camps" must be closed.

"The writing's on the wall - Manus Island and Nauru is over," immigration spokeswoman Sarah Hanson-Young told reporters in Canberra.

Deputy Prime Minister Barnaby Joyce acknowledges some people object to offshore processing but it's necessary to stop people-smuggling.

"I understand that some find it abhorrent but the reality of the policy is this: we have stopped people drowning at sea."

Meanwhile, NSW Premier Mike Baird says the state stands ready to accept more asylum seekers if asked.

"We are opening our arms and happy to play a role if the federal government asks us to take additional refugees," he told reporters in Sydney.

"But again that is a decision that remains with the federal government."