Provincial laws that bar people from growing their own marijuana will certainly be challenged in the courts, and the challenges have a “a decent chance” of success, legal experts say.

The federal cannabis legalization bill, now in the Senate, allows individuals up to four cannabis plants, so long as there aren’t more than four in any given home.

On the other hand, Manitoba and Quebec have said they plan to ban home grows completely.

A legal rule called “federal paramountcy” kicks in when there is direct conflict between federal and provincial law: the provincial law will be declared void, to the extent of the conflict.

Potentially, that’s good news for would-be marijuana growers and bad news for the provinces that want to stop them.

“If you can say that the federal government intended this to be the regime, this is their law, and the provincial government is undermining it, is in conflict with it, then you have paramountcy,” says Margot Young of the University of British Columbia law school. “But you have to show that the federal government had put its mind to this issue, and purposefully, with intention structured a regime that didn’t criminalize that kind of low-level home growing.”

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All provinces other than Saskatchewan have announced at least the basic details of their cannabis legalization plans.

A document about cannabis legalization published in May by the federal justice department states a clear position that provinces can regulate home grows but not actually ban them:

“A lower plant limit may be set in provincial legislation that is consistent with the federal objectives and allows for dual compliance with both provincial and federal limits, however a

complete provincial prohibition on personal cultivation could be seen as frustrating the federal objective and thus be deemed inoperable.”

“This appears to be a fairly clear staking-out of turf,” says Archie Kaiser of the Dalhousie University law school. “I think that’s a problem for the province that would seek to ban personal cultivation.” Tweet This

“I think what the federal government is signaling there is that you can’t totally undermine or frustrate the public policy position that we’ve taken. The federal government is saying ‘We will permit the provinces to do some things which suit them, as long as they’re not completely frustrating our legislation.'”

(Alberta, for example, won’t allow marijuana growing outdoors.)

WATCH: Quebec reveals strict rules for cannabis

1:13 Quebec reveals strict rules for cannabis Quebec reveals strict rules for cannabis

The language is strong, but not as strong as it might be, says Bruce Ryder of Osgoode Hall law school.

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“‘Could be seen as frustrating the objectives of the Cannabis Act’ is language that sits on the fence,” he wrote in an email. “They could have stated more firmly: ‘ … would frustrate the objectives of the Cannabis Act.’ But they didn’t.”

On the other hand. “… that is precisely the sort of indication of Parliamentary intent that is needed to support an argument that a provincial ban on personal cultivation is incompatible with the federal purpose underlying Bill C-45. This statement definitely supports the argument that a provincial ban would be at risk of being ruled unenforceable in the courts.”

Law professors that Global News spoke to were quite certain that the courts would have to deal with the issue.

“These issues are going to get litigated, going to go to the Supreme Court of Canada,” said Joel Bakan of the UBC law school. “It’s hard to tell how the Supreme Court, or any of the courts on the way up, are going to deal with this.”

“People will definitely want to challenge the more restrictive provincial laws, for a host of reasons,” Ryder says. Tweet This

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For Bakan, there is case law on both sides:

A province trying to defend its law is likely to rely on a 2005 Supreme Court case in which a tobacco company failed in a challenge to Saskatchewan’s tobacco advertising laws, which were stricter than the federal ones.

In that case, however, Ottawa and Saskatchewan were going in the same broad direction: discouraging tobacco use.

“The Court (wrote) that Saskatchewan’s law prohibiting retail displays actually furthered the purposes of the federal Tobacco Act, which included discouraging people from consuming a harmful product,” Ryder wrote. ” … The Court was unwilling to impute to Parliament an intent to exclude the operation of more restrictive provincial laws ‘in the absence of very clear statutory language to that effect.'”

Federal law will allow people to grow up to four of their own marijuana plants. GETTY IMAGES

A defendant, on the other hand, would point to the Supreme Court’s 1993 decision on the case of abortion provider Henry Morgentaler. In that case, the court ruled that Nova Scotia’s restrictions on abortion invaded federal jurisdiction.

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“There, the Supreme Court said categorically: ‘This is a federally regulated area,” Kaiser says. “‘You can’t create an offence that so conspicuously attempts to occupy the criminal law legislative power of the federal parliament.'”

“I think it’s got a decent chance,” Ryder says of a challenge. “I’m not sure that it’s a winner, but it certainly has a good chance.”

Penalties for growing pot may not seem worth spending much money on legal fees to avoid — Quebec’s proposed law has a minimum fine of $250. Manitoba has not yet decided on a penalty.

But there’s an elephant in the room, lawyers warn — even a ticket for a minor marijuana offence can lead to a lifetime ban from the United States. And that means that it could make sense for people charged with a minor cannabis offence to spend much more money on legal fees fighting the charge than they ever would by paying a small fine.

(Minor penalties aren’t always an obstacle to a case going to the appeal courts. Gerard Comeau, the New Brunswick man whose acquittal for importing alcohol from Quebec was heard last week by the Supreme Court, faced a fine of $292.50, plus the confiscation of the alcohol.)

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