A law designed to keep Victoria's worst mass murderer in jail until he's dead or crippled is "dangerously unconstitutional", the state's peak body for lawyers says.
Hoddle Street killer Julian Knight, 45, would have been eligible for parole in May after serving 27 years for the 1987 shooting massacre.
But the state government introduced a law into parliament this week to ensure Knight, who killed seven and injured 19 others, is kept behind bars until he dies or can't commit further crimes due to poor health.
Geoff Bowyer, president of the Law Institute of Victoria, says the proposed law is playing politics with people's rights when the parole board would likely never release the mass killer.
"To legislate on the basis of one individual, such as Julian Knight, is a serious and undeniable breakdown in the separation of powers which underpin our justice system, and it sets a dangerous precedent," he said on Thursday.
"That begs the question as to why the government would feel compelled to introduce legislation that is not only unnecessary but also dangerously unconstitutional."
Lawyers are weighing up a possible High Court challenge if the law is passed.
A state government spokesman said it stands by its decision.
"It's open to anyone to attempt a High Court challenge but we believe the law is valid," he said.
Knight killed seven people and injured 19 others when he began randomly firing more than 100 rounds at passing motorists in Melbourne.
He's launched so many legal claims while serving his sentence that he's become a vexatious litigant, requiring him to get court permission before launching further claims.
The legislation, which was introduced into the parliament on Tuesday, severely restricts the circumstances in which the Adult Parole Board can grant Knight parole.
Premier Denis Napthine said earlier this week that it's important to send a clear message even though it's extremely unlikely Knight would be released under the reformed parole system.
"He has a history of issues in prison which shows he has no respect for the health, safety and wellbeing of his fellow man," he said.
Opposition Leader Daniel Andrews has previously agreed that Knight should never be released.
