The Australian Federal Government is playing down the significance of the High Court ruling that found a Sri Lankan refugee could not be denied a visa, despite being deemed a security risk.

The ruling could have implications for more than 50 other refugees who have adverse security assessments and are under indefinite detention.

The High Court said it was invalid to use an adverse security assessment from ASIO to prevent a 36-year-old Tamil man from Sri Lanka being granted a protection visa.

The majority of the court ruled that the regulation which allows ASIO rulings to be used in that way is inconsistent with the Migration Act.

But the Government says the decision does not undermine the Government's approach to asylum seekers.

Attorney-General Nicola Roxon is currently assessing the ruling, with Labor calling on the Opposition to support possible legislative changes to Australia's migration laws in the wake of the decision.

Federal frontbencher Brendan O'Connor says the Government will work to find a balance between issues of national security and its obligations under international refugee conventions.

"I think in the main we have got it right, but the High Court has ruled that one regulation is invalid," he said.

"The Attorney-General has already made very clear she will be considering the implications of the decision and will take the appropriate steps and we would expect the Opposition to do what's in the interests of this country."

Opposition Immigration spokesman Scott Morrison says he will support any new laws to protect national security.

He says the ruling could allow people who are a security risk to get visas.

Refugee advocates say they are concerned that the Government will not accept yesterday's ruling and are calling for the asylum seekers to be released.

Ms Roxon says the High Court explicitly ruled that the Sri Lankan man's detention is valid.

"The judges say the decision now needs to be re-made with respect to this one individual, and they explicitly say - by a majority - that he is to remain in detention while that's done," she said.

Ms Roxon emphasised the High Court did rule in favour of the process used by ASIO, and did not address questions of whether indefinite detention is lawful.

"Previously, the High Court did back the Government's ability to take such action," she said.

"Obviously, there are new people on the court. It can obviously reconsider its position.

"This decision explicitly did not deal with that issue, but we do know that there are other cases that were put on hold while this one was being dealt with, which will no doubt now be heard by the High Court at some point in the future, and the Government will put its arguments in that case."

The chief executive of the Asylum Seeker Resource Centre, Kon Karapnagiotidis, says he is worried about what the Government might do next.

"I'm concerned about the Government already talking about not accepting the umpire's decision and again trying to subvert it by changing the law," he said.

"All the minister has to do is follow the umpire's decision - let these people out and, if not, at least grant them refugee status.

"If he thinks there's genuine evidence to refuse them on grounds of national security he has the power to cancel that visa before they're even released."(ABC News)