The age limit for marijuana should be higher than the age limit for alcohol when the drug is legalized next year, Calgary Mayor Naheed Nenshi told reporters Thursday.

The city's intergovernmental affairs committee is looking at possible rules around cannabis use and how those could affect the municipality.

"I'm very convinced by the science that says the use of cannabis on the developing brain is really a problem, up until early to mid-20s," said Nenshi. "Twenty-five is probably excessive, but I continue to personally advocate that 21 is the right thing to do."

The projected date for legalization, July 1, 2018 — Canada Day — could also use a rethink, said Nenshi.

"I'm probably being overly paranoid about this but I feel like, a public holiday, when you invite hundreds of thousands of people downtown is just not the best first day to try such a major policy change," he said. "So, you know, July 2nd or 3rd maybe."

Nenshi — who was an associate professor at Mount Royal University before becoming mayor, and is currently on leave from that job — says he worries about cannabis use on post-secondary campuses.

"As someone who works with people in that 18 to 22 age range, I don't want to see dispensaries on campus, I'd prefer not to see cannabis lounges on campus," he said. "That's a very personal point of view, that's not the city's point of view but I'd like to see a regulatory regime that makes that difficult."

Calgary Mayor Naheed Nenshi says he'd like to see cannabis dispensaries and lounges barred from post-secondary campuses when the drug is legalized next year. (Robert Short/CBC)

The city doesn't have power over land use on university campuses. Rather, the province does, but Nenshi thinks there's room for discussion.

"We don't ban booze on campus, but we also don't have liquor stores on campus, and I think there are ways we can manage this issue," he said.

Federal officials have said they'd like to see provinces keep taxes low on marijuana to avoid creating black market demand.

"I get that but I also recognize the city is going to be looking at policing costs and enforcement costs and zoning issues that we do not really have the opportunity to recoup, so I would really be interested in figuring out how that revenue sharing on the operating side would work," said Nenshi.

A federal report also said stores already allowed to sell alcohol shouldn't be allowed to also sell marijuana, which will create issues around zoning, said Nenshi.

The province is working to engage the public and municipalities on the subject of marijuana legalization to create a framework for bringing rules into effect.