By Michelle Grattan in Canberra

THE federal government will urgently legislate to enable some of those released from immigration detention to be preventatively detained.

This follows the High Court on Tuesday outlining its reasons for its decision that indefinite immigration detention was unconstitutional. The judgment indicates the decision was unanimous.

Home Affairs Minister Clare O’Neil told parliament late Tuesday: “We are moving quickly to finalise a tough preventative detention regime before parliament rises. The safety of Australian citizens is our utmost priority.”

This is the last full week of the House of Representatives for the year. Next week the Senate sits with the house only due to come back on Thursday to deal with final legislation.

The opposition has been calling for a preventative detention regime.

Opposition home affairs spokesman James Paterson said the High Court reasons had removed the government’s “final excuse not to act”. It was “crystal clear” that a preventative detention regime “is necessary and lawful”.

“If the government introduces one as we have recommended we’ll be highly likely to support it,” Paterson said.

Refugee lawyer David Manne said the court did not suggest there was a need for a new legal regime.

“The High Court makes it clear there are already laws for preventative detention to manage serious risks to the community in relation to people reoffending”, Manne said.

Constitutional expert George Williams, from UNSW, said it would be very difficult for the government to legislate for the whole cohort, but the judgment indicated individuals could be detained under other provisions. This would require a case-by-case approach.

The court says in its judgment a person could, for instance, be detained “under a law providing for preventive detention of a child sex offender who presents an unacceptable risk of reoffending if released from custody.”

The government has released 141 people. One is now missing, and being sought by authorities.

Michelle Grattan, Professorial Fellow, University of Canberra. This article is republished from The Conversation.