Canada's provinces should each get leeway on the way they sell, tax and control marijuana once the drug is legalized by the federal government, according to a new report by the C.D. Howe Institute.

The framework suggested by economist Anindya Sen would create a patchwork of rules across Canada, with different laws governing everything from the stores that can carry the drug to the penalties for selling to underage users.

In this "joint venture," the federal government would monitor the safe production of marijuana for recreational use, while the provinces would oversee distribution, with an eye to meeting public-health goals.

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The report is being released on the same day as a new poll by the Angus Reid Institute that shows support for legalizing marijuana is growing across the country. The poll found that 68 per cent of Canadians agree on the need to "make it legal," a nine-point increase in only two years. April 20 is known as "420" among marijuana enthusiasts, who have waged a long campaign to legalize a drug that has been prohibited in Canada since 1923.

Even though the drug is currently illegal, the Toronto-based Centre for Addiction and Mental Health found that 40 per cent of Canadians say they have used cannabis in their lifetime, including 10 per cent who have done so in the past year.

The federal Liberal government has promised to legalize marijuana, while vowing to take the time to "get it right" as it enacts the major societal change. Key issues to be determined by a coming federal-provincial task force include who will be allowed to produce recreational marijuana, who will get to sell the drug and what kind of controls are needed to try to keep the product out of the hands of children.

A professor of economics at the University of Waterloo, Mr. Sen is urging Ottawa and the provinces to put public-health issues ahead of generating tax revenue as they open the market for recreational marijuana. Both levels of government would tax the product, with Ottawa hitting the manufacturers and the provinces imposing a sales tax on consumers. "The challenge for policy makers is to set tax rates that do not foster an illicit market alongside legal sales," the report said.

In terms of ensuring that new rules are respected, the report added: "As with tobacco, the federal government should establish penalties for illegal trafficking and production, while provinces should have discretion over setting penalties for the purchase and sale of marijuana to minors."

There will be billions of dollars at stake once the drug is legalized, with pharmacies mounting a push to have a right to sell the drug and the Ontario government pushing for the product to be sold at its LCBO liquor stores.

The C.D. Howe report said consumers should be allowed to purchase and carry up to 30 grams of dried marijuana at once, while calling on the government to delay the legalization of edible marijuana products for further study.

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Mr. Sen favours "stand-alone privately owned stores" as the prime location to sell marijuana, arguing that independent retailers are capable of conducting age checks if adequately supervised by provincial authorities. He adds that the provinces may not be willing to make "the necessary infrastructure and staff investments that would be required to sell marijuana at provincial liquor stores."

Angus Reid found the most popular places to sell marijuana are licensed dispensaries that carry only cannabis products (with 69-per-cent support), followed by provincial stores (with 67-per-cent support).

Only 23 per cent of respondents supported the right of citizens to grow and sell their own marijuana, and only 6 per cent said Canadians should be able to grow an unlimited amount of plants for personal use and/or sale.

"There seems to be broad consensus that if people are going to be growing it at home, Canadians don't want them selling it," Angus Reid said.

The Angus Reid poll of 1,522 Canadian adults was conducted online between April 13 and 17. A probability sample of this size would carry a margin of error of 2.5 percentage points, 19 times out of 20.