CRIMINALS convicted of terrorism offences could be locked up for life.
The proposal by Prime Minister Malcolm Turnbull was backed on Friday by state premiers at COAG talks in Sydney.
Mr Turnbull said there was unanimous support around the table for the move, which would allow indefinite detention of terrorists who posed an ongoing threat - in the same way that unreformed pedophiles could be kept in the prison system.
Concerns about the proposed law change were raised even before the meeting ended.
Law Council of Australia President Duncan McConnel said it would be "a very difficult matter" to assess whether someone represented a danger to the community.
"The means by which government would assess whether a person is a danger to the community are likely to be subjective," he said.
"The risk of abuse of the power or the wrong application of the power is therefore very high."
Mr McConnel said the council wanted to be satisfied about how such assessments would actually be completed and "against what factors".
He urged state leaders to carefully consider, before introducing the laws, any "alternative proposals that would not see people being detained arbitrarily".
Referring to Thursday's tax talks between Federal Treasurer Scott Morrison and the state treasurers, Mr Turnbull said there would be more discussions before a decision on tax reform was made by March next year.
The government refused to back any plan without consensus from state governments, which did not eventuate.
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