Marijuana advocates from across B.C. are puffing en masse this afternoon to protest the legal prohibition of the drug.

The so called "4/20" event, held each year on April 20, is the high holiday for pot smokers.

Smoke-ins will be held in several major Canadian cities including Victoria, Toronto, with the largest expected in Vancouver.

Organizers expect up to 15,000 people to turn out at the Vancouver Art Gallery starting at noon.

Jacob Hunter said the main theme of this year's event is to get young people out to vote in hopes of defeating Stephen Harper's Conservative government.

"For every one young voter there are voters over the age of 65, and that's not helping us legalize marijuana," he told "We want to tell them to vote for anyone but the conservatives."

This is the first rally to be held in Vancouver without B.C.'s self-proclaimed "Prince of Pot" Marc Emery.

Emery, who is currently serving a five-year sentence in the U.S. for selling marijuana seeds to Americans, was denied a transfer to Canada last week.

As in year's past, the Vancouver police plan to have a "low key" presence at the rally.

Const. Lindsey Houghton said officers are just there to keep the crowds safe and make sure the party doesn't spill out onto downtown streets.

Hunter said authorities recognize their "unique form of protest," and have never had a problem with their political expression.

"People who are drunk tend to get rowdy whereas people who are smoking pot relax and eat pizza," he said. "Everyone just has a great time."

Check back to CTV British Columbia later this afternoon for a photo gallery of the event...