If prime minister-designate Justin Trudeau intends to make good on his promise to legalize marijuana in Canada, he might want to start by looking to Washington State, where recreational marijuana stores have been operating for over a year.

King County sheriff John Urquhart says the biggest lesson learned in Washington State is that once pot becomes legal, cities should not have the power to use zoning bylaws to completely ban weed shops.

"There are several cities in the state and in King County that have outlawed marijuana stores, and that's a big problem as far as I'm concerned," Urquhart told CBC.

"One of the premises of legalized marijuana is to get the grey market and criminals out of it," he continued.

"If someone has to drive 30 miles to buy their joint, they're not likely to do that. They're going to buy it from their old dealer who's not licensed, who's not paying taxes."

Three separate silos

Urquhart says Washington has created strong licensing rules around production, distribution and the retail sale of marijuana, which help regulate the industry while keeping the criminal element out.

"In Washington those are three separate entities in three separate silos. So you can't be a retailer and a distributor, and a grower. You have to be one of those three things."

In 2012, voters in Washington State voted 55 per cent in favour of legalizing recreational marijuana. The new law allows adults over the age of 21 to possess up to an 28 grams of marijuana.

War on drugs wasn't working

Urquart, who is a former narcotic investigator, says he supports legalization because "the war on drugs just wasn't working."

And so far says Urquhart, none of the dire scenarios of increased crime and increased addiction have come to pass.

"Marijuana use among teenagers is actually down slightly in Washington state since legalization." claims Urquhart.

"The underground economy, organized crime has not taken over the retail or manufacture or sales at all. None of the bad things that were predicted by the opposition have happened."

"That being said we don't know how this is going to work out in the long term. I call this a giant social experiment, and we don't know what the long term effects of all this are going to be."