A Canberra judge on Tuesday jailed Fakatounaulupe Ngata, 37, for three years for the aggravated robbery on October 4 last year.

The former Rebels Canberra sergeant-at-arms will be eligible for parole in May.

Ngata appeared for sentence in the ACT Supreme Court after he last month pleaded guilty to one charge of aggravated robbery.

The court heard Ngata and two other alleged Rebels members confronted two men in motorcycle clothing at an entrance to Belconnen Mall about 6pm.

Ngata said: "Did you know this is Rebels territory?" before he assaulted and stripped one of the rival gang members of a T-shirt emblazoned with the word FINKS.

The theft of the T-shirt constitutes aggravated robbery as Ngata was in company and used force.

Ngata later burnt the shirts.

Ngata had been the gang's Canberra sergeant-at-arms at the time of the offence.

The court has previously heard that Ngata had since resigned from gang, had returned his colours to the Rebels Outlaw Motorcycle Club in March, and wanted to live a "straighty 180 life".

He said he had severed links with the bikies and had no intention of returning.

The court hears Ngata had been previously convicted of 23 offences, mostly for driving, but also kidnapping and forcible confinement.

Justice Richard Refshauge, in handing down sentence, noted the offence did not involve weapons and had been a targeted attack, not on a random member of the public.

But the judge said that inter-gang rivalry spilling into public posed a public risk.

"It was an unprovoked bashing because of a perceived impropriety of the entry of the victims into so-called Rebels territory," Justice Refshauge said.

"Notwithstanding the victims were perfectly entitled to be in Canberra and at Belconnen mall."

Justice Refshauge sentenced Ngata to three years jail, backdated to take into account time spent in custody, with a non-parole period of 18-months.

Back-up charges of affray and participating in a criminal group were dismissed.