Manitobans who want to grow their own recreational cannabis may now have legal ammunition to use in any future court challenge of the province's home-growing ban.

The Quebec Superior Court struck down that province's ban on home cannabis cultivation on Tuesday. In its decision, the court ruled the provincial ban was unconstitutional because it infringed on the federal government's jurisdiction over criminal matters.

"[T]he effect of the provincial provisions is a step backward, as though the new federal law aiming at accessibility and legalization of cannabis had never existed," Justice Manon Lavoie wrote in her decision, translated from the original French by a bilingual CBC journalist.

Manitoba and Quebec are the only provinces that completely banned the growing and possession of cannabis plants in a residence following the legalization of recreational pot last October.

So far, only one person has been charged for cultivating cannabis in a residence since the Liquor, Gaming and Cannabis Control Act came into effect last fall, a Manitoba government spokesperson told CBC News.​

Under the federal government's rules, Canadians are permitted to grow up to four plants in their home for recreational use. The rules are clear that provinces have the right to create "additional rules for growing cannabis at home, such as lowering the number of plants per residence," but do not explicitly say provinces can ban home growing outright.

By declaring the sections of Quebec provincial law prohibiting home cultivation invalid, the court has declared that people there are free to grow their own.

Lawyers in Manitoba say that could open the door to anyone here who wanted to challenge the legal validity of this province's ban.

"Somebody in Manitoba might take a look at this and say, 'Hey, there's a precedent out there,'" said Jamie Jurczak, a partner with the Winnipeg law firm Taylor McCaffrey.

Constitutional violation

The applicant in the Quebec case, Janick Murray Hall, argued the ban violated sections of the federal Constitution Act of 1867, which lays out the boundaries of federal and provincial authority. It gives the federal government sole authority over criminal matters, said Chris Gamby, communications director for the Criminal Defence Lawyers Association of Manitoba. 

In this case, the Quebec law was found to have re-criminalized something which the federal government had chosen to allow.

"For the province to then come in and say, 'Well, you're not allowed to even grow one plant' … they're sort of undercutting what the intention of the federal Parliament was," Gamby said.

Manitoba's ban imposes a $2,542 fine on anyone caught growing up to four plants in their home. When it was announced last year, legal experts warned that the province could be crossing the line by imposing such a significant fine.

Courts look at a number of factors to determine whether a law falls within provincial or federal jurisdiction, including whether failure to follow a provincial rule would result in punitive measures. If so, the legislation may be considered a criminal law.

Courts may also ask if the province's law is more concerned with legislating the possession of the property itself, or mitigating harm caused by possession of the property.

The Quebec court concluded that the effect of the province's legislation "constitutes a complete ban on a practice" and that "the provincial legislator intended to reprimand a now lawful activity, and ultimately, to strengthen criminal law."

The lawyer for the applicant in the Quebec, Julien Fortier, told CBC News there is a chance the provincial government could appeal the ruling, or rewrite the law to make it constitutional. 

Fortier called Justice Lavoie's ruling "very technical" and noted the case "was strictly about the ... constitutional law." 

Success not guaranteed

The fact the law in Quebec has been struck down, however, doesn't mean a potential challenge in Manitoba is guaranteed to succeed, because the wording of the legislation is not identical in the two provinces.

"The differences in legislation can mean different determinations. It's those nuances that can sometimes make or break a decision," Jurczak said.

There is also no guarantee that a person charged for growing at home would want to go through the ordeal of fighting the provincial ban in court.

"Taking a court case through to a challenge like this, knowing that there's potential for appeal at many levels, that is a long endeavor," Jurczak said.

"Some people might just not be interested in spending the time or the money that would be required to do that."