An annual day of celebrating cannabis culture is ramping up into mainstream political activism as the pot-smoking 420 movement takes on marijuana prohibition with rallies across Canada.

According to a Facebook event, hundreds will gather at Victoria Park in Brantford to smoke marijuana and protest current pot laws. The event is not sanctioned by the city.

In Ottawa, police are advising motorists to steer clear of Parliament Hill in the national capital as a large demonstration is expected for the annual April 20 event, when pot activists traditionally partake at 4:20 in the afternoon.

The 420 moniker dates back to the pot culture of California in the early 1970s, but it became formally attached to April 20 when a group of Vancouver activists held the first day-long rally in 1995.

Anti-prohibition activist Jodie Emery says recent legalization in two U.S. states has opened the eyes of governments and businesses to the financial benefits of a legal trade in marijuana.

And she says that has given the annual 420 rallies -- which have now gone global -- a renewed emphasis on influencing government policy.

As Emery puts it, "we've won over the Man and the establishment."

With files from CTV Kitchener