Australia needs powers to ban foreign fighters for up to two years to stop dangerous terrorists and jihadi brides from returning until authorities are ready to deal with them, Home Affairs officials insist.
But legal experts have slammed the underpinning legislation as an embarrassing "dog's breakfast".
Under the changes introduced to federal parliament last month, Australian foreign fighters who want to return home could be blocked from entering the country for up to two years by a ministerial decision.
The minister could revoke the exclusion order to allow someone to enter Australia under a return permit, which may include conditions relating to when and how the person enters the country.
The Home Affairs Department told parliament's joint committee on intelligence and security there was no existing tool that allowed agencies to manage the return of foreign fighters when there wasn't enough evidence to prosecute them, and that the situation now was different to when control orders were updated four years ago.
"The caliphate is diminished, the last of the fighting is about to end and the foreign fighters are now in the position where they're looking to return," commonwealth counter-terrorism coordinator Linda Geddes told the committee in Canberra on Friday.
"It's a new tool that we're looking to bring in to manage the return, effectively, in a controlled way, of some very dangerous people that will come back to Australia."
She said it could also apply to women who had travelled to the Middle East to marry Islamic State fighters and now wanted to come home.
"We may not know when a jihadi bride returns," Ms Geddes said.
"We will have all the alerts in place at borders but it will mean that the agencies, the law enforcement and security agencies may not have in some circumstances enough time to put a risk management program around that person."
But the Law Council of Australia and the Australian Human Rights Commission say the law should not be passed in its current form.
"This is a dog's breakfast," Law Council president Arthur Moses told the committee.
"It's quite embarrassing that this type of legislation would be put before the parliament."
The legislation went against two High Court rulings that the minister could not stop citizens from returning to Australia, he said, and it should instead follow the UK model where a court has to make the exclusion order.
The UK example offered greater transparency and better protections both for the minister and the person affected by the order.
"We want to make clear again: this is not a soft-on-terrorism approach," Mr Moses said.
"This is about being smart. You don't pass legislation when you know it's going to be invalid. You pass legislation that works."
The Law Council also has concerns the law would apply to children as young as 14, and that there is no restriction on a minister making a rolling series of orders that would be a "sham arrangement ... to permanently deprive an individual from coming back to the country".
Home Affairs says there are about 100 Australians still actively involved in the Syria and Iraq conflicts who may pose a threat when they return home.
Australian Associated Press