If you’re 18, and try to buy recreational marijuana in Ontario next summer, you’re going to get carded and told to come back when you’re 19.

That will probably seem frustrating, since the federal rules for recreational pot set 18 as a minimum age, and at least two other provinces, Quebec and Alberta, have said they will set their cannabis ages to match that.

READ MORE: 19 will be the minimum age for legal cannabis use in Ontario

But in Ontario (and potentially six other provinces where the drinking age is 19, and it may be tempting for regulators to set the cannabis age there as well), 18-year-olds will fall into a weird grey area. In Ontario’s case, the worst that can happen is that police might take your pot away.

“Our proposed approach will prohibit youth under 19 from possessing or consuming recreational cannabis, regardless of where it was purchased,” provincial Ministry of the Attorney General spokesperson Nadine Ricketts wrote in an e-mail. “This will allow police to confiscate small amounts of cannabis from young people without unnecessarily bringing them into contact with the justice system.”

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Can you mail-order your pot from Alberta or Quebec? Possibly.

“Are they just going to say ‘If you live in Ontario, we’re not going to accept your identification and we’re not going to mail you anything?” asks Jenna Valleriani, a University of Toronto PhD student who studies marijuana dispensaries.

What about growing your own? (As far as the feds are concerned, you’ll be able to start a small marijuana farm on your 18th birthday, with no size restriction on your four plants. Marijuana plants can grow to be the size of small trees.)

The provinces would be open to constitutional challenge if they tried to stop that, says Paul Lewin, a Toronto lawyer who specializes in marijuana cases.

“The province shouldn’t be prohibiting growing — that’s not their purview,” he says. “They’ve been given distribution. There are federal criminal law rules concerning growing that prohibit growing beyond four plants. I think that would be outside the jurisdiction of the province, to prohibit growing.”

WATCH: Alberta Justice Minister Kathleen Ganley announced Wednesday that the minimum age for purchasing cannabis under the new legalization framework will be 18, same as with alcohol.

1:10 Minimum age for buying legalized pot in Alberta will be 18 Minimum age for buying legalized pot in Alberta will be 18

In a leaked discussion paper, Ontario’s police and corrections ministry flagged the issue of legal pot and 18-year-olds as a potential headache for police.

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Sales to, and possession by, people 17 and under would be a criminal matter. But 18-year-olds will have to be covered by a provincial law, like a traffic law, written for them specifically and prosecuted like traffic charges in a separate court system for provincial offences. This would have the effect of “increasing the complexity of enforcing for police officers,” the report noted.

“I’m not sure how Ontario is going to propose to fill that gap,” Valleriani says. “It would be really odd if they created a whole set of regulations that just applied to 18-year-olds.”

WATCH: The New Brunswick government has become the first Atlantic province to reveal its plans for the legalization of marijuana. Adrienne South has more information on the details of the plan.

2:05 New Brunswick creates Crown corporation to oversee marijuana sales New Brunswick creates Crown corporation to oversee marijuana sales

New Brunswick, which has announced some details of its cannabis legalization plan, hasn’t committed itself on a minimum age, although a provincial commission recommended 19, that province’s drinking age.

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(In the Ottawa Valley, Ontario 18-year-olds have for many years crossed the river to Quebec to buy alcohol legally; it’s reportedly becoming clear that exactly the same thing will happen with marijuana come next July.)

“I don’t know if there’s a conflict between the laws, but it does seem like there’s one group that’s kind of caught in the middle,” Lewin says.

“It would have made a lot more sense to have it all synched up because it does seem a bit ridiculous. If you can buy federally, nothing is stopping you from purchasing it in another province, or purchasing it by mail order, if you’re medical, but you can’t buy it from the store, which does all seem a little stupid. The laws don’t conflict, but it does seem a little stupid.”

Ontario’s Ministry of the Attorney-General didn’t respond to questions sent last week by Global News.

Last fall, the Canadian Medical Association recommended a cutoff at 21, based on the science of the developing brain. (They said that they would have preferred to set it at 25, but recognized that that was unrealistic.)

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On the other hand, the federal Liberals have said that their main goal in legalizing marijuana is to eliminate the black market, and it’s clear that the higher the minimum age, the less successful that will be.

“It’s not practical at all – it doesn’t make any sense,” Lewin says. “The public wants clear rules, not weird exceptions.” Tweet This

WATCH: With the clock ticking towards legalization, the B.C. government has announced a public consultation process on how marijuana will be sold and regulated in B.C. Grace Ke reports. 1:40 Public consultation process begins over legalized marijuana Public consultation process begins over legalized marijuana