Former Army chief Peter Leahy believes dual Australian-Syrian citizens should be prevented from returning here after fighting in Syria's bloody civil war.
"How can you be an Australian, go off and fight in Syria, in some cases for al-Nusra who are linked to al-Qaeda, and then come home?" he told Sky News on Monday.
Lieutenant-General Leahy was responding to a call by former foreign minister Bob Carr who revealed he tried to have the previous Labor government change the law.
Mr Carr said about 200 Australians had gone to Syria, some to deliver aid and some to fight.
In government he received advice that nothing could stop them returning to Australia.
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Professor Leahy says the law should be examined to see what could be done to stop dual citizens going to Syria in the first place.
"And if they become involved in some of this really nasty work that's going on, let's not have them back in the country."
He questioned whether dual citizenship works.
"Can you be loyal to two countries - I'm not sure you can be."
