19-year-old Mr Bridgeman travelled to Bali in March last year and was reported missing when he failed to return home.

He had, in fact, travelled to Syria to undertake aid work with an organisation called Live Updates from Syria.

The cancellation of his passport comes as Mr Bridgeman was about to return to Australia.

According to Mr Bridgeman's lawyer, Alex Jones from Bosscher Lawyers, his passport was cancelled after the government felt he "would be likely to engage in conduct that might prejudice the security of Australia or a foreign country" and that its cancellation would "prevent him from engaging in the conduct".

But Mr Jones has hit back at these claims, saying there was no evidence Mr Bridgeman had undertaken any unlawful acts while in Syria.

"We can't see any real basis for this decision," he said.

"There doesn't seem to be any logic."

The news comes as a particular blow for Mr Bridgeman's parents as their son was making preparations to come home.

"He went there out of a moral obligation to assist what are some of the world's neediest people," Mr Jones said.

"Oliver's parents are obviously quite upset at the decision, they are disillusioned, they are feeling betrayed because they were cooperating entirely with the authorities over the course of the last 12 months."

Mr Jones said Mr Bridgeman had been offered a temporary travel visa, but would need to get to Turkey to obtain it, requiring him to cross the border from Syria.

"The government have offered a temporary travel visa, the problem with that he has to make his way to Turkey," he said.

"If you cross a border without a passport you are liable to criminal offences."

Mr Jones said the next step would be to lodge an appeal to have the decision overturned.

Foreign Minister Julie Bishop refused to comment.