Video of three correctional services guards grabbing a 13-year-old boy by the neck and forcibly stripping him is appalling, the Northern Territory Children's Commissioner said.

The ABC broadcast the 2010 footage this week after a Supreme Court justice upheld a prior ruling that the guards did not use unreasonable or excessive force.

It shows three guards entering a small cell in Alice Springs, taking the child by the neck and turning his head away before dropping him face-down onto a mattress.

The guard pins him by the head as another guard pulls off his shorts and underpants, then holds him down with his knees across his naked buttocks.

Afterwards the boy is seen stalking around the cell and throwing his torn-up mattress at the CCTV camera in visible distress.

The boy had been classed as at-risk and needed to be dressed in a non-rip gown, Justice Peter Barr ruled, and was apparently a known "spitter".

Restraint is only ever used as a last resort in situations where there is a threat to an inmate or staff, said Corrections Minister Robyn Lambley.

But at that point he was not a threat to anyone, said NT Children's Commissioner Dr Howard Bath.

"Violently grabbing and putting the kid down with knees and hands around the neck and on the buttock, stripping him naked, is hardly a therapeutic response; it's likely to harm the child," he told AAP on Friday.

The action appeared designed to humiliate the boy, and was "appalling practice", he said.

Justice Barr said the force used did not appear to be excessive, describing the actions as low-level physical violence.

The video only shows a small portion of the incident, said Minister Lambley, excluding the threats to self-harm and violence the boy displayed before the incident.

"The youth detainee featured in the vision has been found guilty of more than 50 criminal offences, many of which were violent acts, over the past five years," she said.