Federal Attorney-General George Brandis expects his state and territory counterparts to back the Commonwealth's proposal for convicted terrorists to be kept in jail once their sentences have finished, if they are deemed to still pose a threat to the community.

The plan, announced by Prime Minister Malcolm Turnbull and Senator Brandis last week, would involve periodic reviews of the threat posed by a convicted terrorist, with judges given the discretion to keep them behind bars.

The Attorney-General said he expected support for the policy, which was similar to laws keeping sex offenders off the streets.

"It is, as I say, modelled on existing — or some existing state legislation — in relation to other categories of serious crime," Senator Brandis said.

"I am expecting that all of my colleagues, all of my counterpart attorneys-general will agree to this because it's a very important measure from the point of view of community safety."

Civil libertarians have raised concerns with the proposal, arguing it avoided dealing with the real issues in combating terrorism.

Senator Brandis disagreed, and said it was indicative of the Government putting in place measures to stay ahead of the threat.

Sorry, this video has expired Turnbull announces 'decisive, necessary' anti-terrorism measures

He would not comment if such a proposal would have kept prisoners such as Ahmed Elomar, the brother Islamic State terrorist Mohammad Elomar, behind bars.

The Attorney-General said he would not comment on specific prisoners, or on Ahmed Elomar's case.

"This legislation will only apply to serious terrorists coming to the end of a sentence of imprisonment, who continue to pose in the eyes of a judge on the basis of admissible evidence including psychological assessments and so forth, an unacceptably high risk to community safety," Senator Brandis said.