Two Victorian mental health patients have won their right to refuse compulsory electro-convulsive shock therapy, in a move heralded as a victory for human rights.

Legal Aid brought a test case on behalf of the two patients, PBU and NJE, diagnosed with schizophrenia after both were ordered to undergo electro-convulsive shock therapy by the Mental Health Tribunal.

Legal Aid began representing PBU after he had the therapy, or ECT, without his consent in 2017, and NJE was facing 12 sessions - ordered at a hearing where she didn't have a lawyer.

The pair initially failed in an appeal to the Victorian Civil and Administrative Tribunal, which upheld the tribunal's decision that they have the therapy.

But the Supreme Court overturned the ruling on Thursday, finding VCAT misapplied the law over whether the patients had capacity to decide if they wanted ECT.

"What the decision means is that they will not receive ECT pursuant to these orders," Victoria Legal Aid's Hamish McLachlan told reporters outside court.

"This is a really significant case for the thousands of mental health patients in Victoria who face compulsory mental health treatment each year."

Mr McLachlan added the case was not about whether ECT was good or bad.

"What the case was about was ensuring when people are facing having ECT without their consent, that their human rights are upheld."

Mr McLachlan said the decision provided clear guidance that mental health patients had the same fundamental human rights as everyone else, and decisions about their treatments must be made accordingly.

The case could have implications for the 700 compulsory electro-convulsive therapy applications considered by the tribunal in Victoria each year.

"It was one of the most traumatic days of my life, when I was taken into the ECT room and held down on the bed. I didn't know I was going to have ECT," PBU said in a statement about his treatment last year.

"The most terrifying aspect of having ECT is that I didn't know what state I would be in after."

Victorian Mental Illness Awareness Council CEO Maggie Toko was "delighted" about Thursday's decision.

"People with mental illness can now feel more secure that their views about ECT will be respected and upheld," she told reporters.

"We hope this ruling will reduce the amount of compulsory ECT and moves us towards a day when Victoria stops using this procedure on people against their will."

She said the treatment remained controversial and could lead to cognitive and memory loss in some cases.

"Some people tell us that ECT saved their life, and some people tell us that ECT ruined their life. Both experiences are valid because ECT affects people differently," she said.

"Our position is that people should only have ECT if it is their own choice and they know all the risks."