Ontario's highest court has ruled that a three-year mandatory minimum sentence for possessing a loaded prohibited gun is unconstitutional.

The Ontario Appeal Court ruling strikes down a plank of the federal Conservatives' 2008 omnibus bill, which raised the penalty from one year.

The court found a three-year prison sentence to be "cruel and unusual punishment" for a first offence.

The problem, the court says, is that the current law does not discriminate. For example, a person keeping a restricted firearm with ammunition in their cottage when their licence requires it to be stored in their home would face the same minimum sentence as a person on the street with a loaded gun in a back pocket and the intent to use it.

The court says the ruling has no significant effect on sentences for people engaged in criminal conduct or who pose a danger to others, saying they should continue to receive sentences to emphasize deterrence and denunciation.

The Appeal Court heard six appeals together in February because each involved a constitutional challenge to a mandatory minimum sentence for various firearm offences.

Deterring crime?

In a statement following the decision Tuesday, Justice Minister Peter MacKay said the federal government is reviewing court findings in order to determine its next steps. "We will continue to defend the constitutionality of mandatory prison sentences for serious criminals," MacKay said.

"Mandatory prison sentences show Canadians that the rights of criminals will no longer trump the rights of victims of crime," he added.

The minimum sentence was originally struck down last year by the Ontario Superior Court in the case of Leroy Smickle, who was caught alone in his boxers in his cousin's apartment posing with a loaded handgun while taking pictures of himself to post on Facebook. Police burst in, looking for his cousin.

Federal government lawyers had argued in support of the law, pointing to a spate of gun violence in 2005, which first prompted Ottawa to propose the stiffer penalties.

Critics in the legal community, however, say mandatory minimums don't reduce crime and do more harm than good.

Dirk Derstine, one of the lawyers who fought the Crown on the appeal, argues that minimum sentences don't work as a deterrent to crime.

"I think there's a kind of seductive appeal to the idea that all we have to do is ratchet up sentences and these people will, quote, unquote, get the message and stop doing this kind of behaviour," Derstine said. "The difficulty with that is that it's seductive, but it's also incorrect."