VANCOUVER - As a former high-profile U.S. federal prosecutor, John McKay stands behind actions that had Canada's "Prince of Pot" arrested, indicted and ultimately sentenced to five years in an American prison.

But he does agree with Marc Emery on one point: marijuana should be legal.

McKay sat side-by-side with the cannabis activist's wife, Jodie Emery, on Wednesday as he joined the growing call from British Columbia to end pot prohibition in favour of the drug's regulation and taxation.

"We do share, I think, a belief that the underlying policies are wrong," he told a public forum in Vancouver on throwing support to a coalition spearheading a public education campaign that's been growing steady momentum.

Emery's decision to sell marijuana seeds by mail to U.S. customers, including minors, was a "tremendous mistake," McKay said, and it has barred the man from gaining the platform he needs to make change.

McKay was Washington state's chief law enforcer for five years, and that's where he fully witnessed how current policy fuels gang violence through the cross-border drug trade, he said. He now teaches law at a Seattle university.

"As a person who is knowledgeable of the facts underlying our failure in marijuana prohibition, I am free now to speak out."

Since October, four former B.C. attorneys general, several Vancouver mayors and a host of police and health officers, academics and the Brazil-based Global Commission on Drug Policy have challenged provincial and federal governments to reform Canadian laws.

Jodie Emery, an advocate herself who has spoken on her husband's behalf since he went to prison in 2010, said she welcomed McKay's support.

"I don't believe my husband should be in prison, I still miss him terribly. But I understand that this law, the prohibition of marijuana, forces police to continue to arrest people and put them in prison," she said.

"When we get people who are on the frontlines, who saw the damage done, admit the policy needs to be changed, I think that's always a wonderful thing."

Speaking two days before the annual 4-20 celebration — a counterculture holiday where marijuana users gather to smoke weed — McKay said Canada's policy is out of step internationally.

He said that's harming citizens on both sides of the border.

Ballot initiatives in Washington and Colorado will ask voters in November if they agree to legalize the possession of one ounce or less of marijuana for adult use.

Tax proceeds could reach half-a-billion dollars in one state on its own. The money would be earmarked for education, treatment and to ensure it stays out of the hands of minors, McKay said.

"It would be regulated at every point of its production, its sale, its taxation, its content and the use of its proceeds," said McKay, who is co-sponsoring Initiative 502 in Washington.

Medical marijuana is legally permitted in 16 states and the District of Columbia, while 14 states are moving to decriminalize pot possession in some form.

He rejected arguments that the U.S. government would take punitive action against Canada for reforming its laws.

"There's been talk that somehow there would be retaliation by the United States if there were regulation and taxation scheme here. Hardly," he said. "The same debate, perhaps further along, is occurring south of the border."

A spokeswoman for Conservative Justice Minister Rob Nicholson has repeatedly said the federal government has no intention to decriminalize or legalize marijuana. B.C. Premier Christy Clark has previously said she is deferring to the feds.

Geoff Plant, who was B.C. attorney general from 2001 to 2005, said he believes the campaign is building momentum starting in city neighbourhoods that will eventually reach Ottawa.

He doesn't expect pot to be legalized under the current Conservative regime.

"But I think there's a realistic chance it could be within the term of office of the next prime minister of Canada," he said. "That's a target that I think has an aura of reality about it that I think we should commit to."

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