Canadian Prime Minister Justin Trudeau has called on Canada’s newly appointed Minister of Justice and Attorney-General Jody Wilson-Raybould to look into implementing marijuana legalization in the country.

In a mandate letter written to Wilson-Raybould, published on Friday, Trudeau asked her to collaborate with other ministers to “create a federal-provincial-territorial process that will lead to the legalization and regulation of marijuana.”

But challenges involving the regulation of edible marijuana, and drug-impaired driving, could still hinder the legalization process, Lewis Koski, Colorado’s director of the Marijuana Enforcement Division, told the CBC. Colorado is one of four U.S. states where recreational marijuana use has been legalized.

“It’s going to be a lot harder to implement than you think. It’s going to take a lot longer to do it. And it’s going to cost more than you think,” Koski said.

Read the full mandate letter here.

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