James Haberfield, 22, became the first person under new Victorian laws on Wednesday to be slapped with mandatory treatment and monitoring for offenders who attack emergency workers.

However he avoided a minimum six-month jail term also required under the new laws, which came into effect last October.

On January 29 this year, Haberfield returned to Melbourne after the four-day Rainbow Serpent music and arts festival during which he consumed "a cocktail of drugs" including ecstasy, ice, MDMA and ketamine.

He knocked on the door of a Coburg home, walking inside and terrifying the residents, who he did not know.

An ambulance came to collect Haberfield, staffed by two paramedics.

While he was being cared for in the rear of the vehicle and in an "acutely psychotic state", he became aggressive, punching a female paramedic in the face, wrapping his arms around her and squeezing.

The victim screamed as Haberfield pinned her to the rear corner of the ambulance.

The paramedic driving the ambulance sedated him with midazolam before he was taken to Royal Melbourne Hospital, where he underwent treatment for more than a week.

Magistrate Simon Zebrowski said Haberfield's impaired mental state that day wasn't solely due to self-inflicted intoxication as he had pre-existing autism spectrum disorder and a major depressive disorder.

A psychiatric expert said he would have an elevated risk of suicide while in custody.

Instead, Mr Zebrowski said sending the "mortified, dismayed and deeply ashamed" young man to jail "would have a disproportionate and catastrophic effect" on his future.

Haberfield was given an 18-month community corrections order and must undergo mandatory treatment.

Premier Daniel Andrews responded to the verdict, urging the state to appeal the sentence.

"Our thoughts are with the victims of this completely unacceptable attack," he said.

"The DPP should give urgent consideration to appealing this matter."

Victorian Ambulance Union secretary Danny Hill said he was furious about the ruling.

"I don't think I've been angrier in a long, long time," he told 3AW's Neil Mitchell.

"Today, I'm dumbfounded."

The union boss said the ruling undermined the mandatory sentencing for assaulting emergency service workers, and there "absolutely" must be an appeal.

"In almost every case that a paramedic attends a patient will have some form of mental health history," he said.

"If that's an excuse in all cases ... then this legislation is a dud.

"It's not mandatory sentencing. It doesn't work."

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