Abdul Nacer Benbrika became the first Australian convicted of leading a terrorist organisation and was jailed for 15 years in 2009.

The man who encouraged a bomb plot targeting the MCG completed his full prison sentence last year was ordered by Victorian Supreme Court Justice Andrew Tinney to remain behind bars until November 2023 because of ongoing fears he is a risk to the community.

Lawyers backing his continued detention told a Victorian Court of Appeal hearing on Wednesday that even a small risk was unacceptable.

"Even a modest risk of a serious outcome would be, in the circumstances, an unacceptable risk to take," Andrew Berger, representing Home Affairs Minister Karen Andrews, said.

Earlier this year Benbrika took his challenge to the High Court, arguing the Supreme Court didn't have the power to make the order locking him up beyond his original sentence.

But that case was knocked back.

Benbrika's lawyer Dan Star QC said the decision to continue holding him behind bars was made partly based on "inherently unreliable" notes taken from a deradicalisation program Benbrika had participated in behind bars.

Mr Berger said the minister's position was the records not only showed a failure by Benbrika to renounce his extremist beliefs but that his support for the ideology that led to his offending was continuing.

Benbrika, who is now in his 60s, came to Australia from Algeria when he was 29. He began hosting Islamic theology classes from about 2002, including for others convicted alongside him.

The self-proclaimed Islamic cleric has expressed past admiration for Osama Bin Laden and was leading a group in a plot to kill "non-believers" in an effort to convince the Australian government to withdraw troops from Iraq.

The appeal judges noted Benbrika had not harmed anybody and nothing he had done had led to any risk of a person being harmed, prompting questions about why he is now considered an unacceptable risk to the community.

Mr Berger said the fact no harm had been done did not minimise the seriousness of Benbrika's role.

"He was leading a young group of men and encouraging them to commit very serious offences, including on the MCG, and the fact they hadn't actually succeeded at the point of being arrested is not beside the point, but it doesn't minimise the significance of it," he said.

The three judges hearing the case will hand down their decision at a later date.

Australian Associated Press