A coalition of groups concerned about the health risks associated with marijuana is calling legalization a "dark day for Canada."

Members of Smart Approaches to Marijuana Canada, Air We Share and Airspace Action on Smoking and Health tried to share the message from the steps of the Vancouver Art Gallery on Wednesday.

Coalition spokesperson Pamela McColl said she believes legalization normalizes a dangerous substance and positions Canada to be the base of the marijuana industry's global expansion.

"It is a very, very dark day for Canada," she told a crowd of gathered media.

"The damage that is going to ensue from this policy change will be horrendous in terms of drugged driving, cognitive damage to children, more addiction, more costs. The list goes on," she said.

McColl said she wants to see regulation tightened to ban smoking marijuana from any multi-unit residence and anywhere that children live.

"It's Canada Went to Pot Day," she declared.

Pro-pot activists said claims presented by the groups were not all backed up by research. (CBC)

'Too far, way too soon'

Kevin Sabet, a former senior adviser at the White House Office of National Drug Control Policy, said Canada's drug policies have effects beyond its borders.

He compared "Big Cannabis" to "Big Tobacco" and warned that legalization will mean the rise of large cannabis corporations that don't have an interest in public health.

"We're going way too far, way too soon," Sabet said.

The coalition announced the launch of a new website Wednesday for filing complaints about the law and reporting violations at Potwatch.org.

Steps away from the protest, people purchased pot at a makeshift booth. (CBC)

'Proper legalization'

Across the square, a group of pro-pot advocates also shared an anti-Big-Cannabis message from a makeshift booth selling marijuana and displaying plants.

Dillon Mcardle said the sale was an act of civil disobedience intended to draw attention to the monopoly forming in the industry.

"We're protesting for the proper legalization of cannabis. We want to see free weed for medical needs and equal rights for every Canadian citizen to grow it, smoke it and sell it, of course over the age of 19," said Mcardle.

Pot activist Anil Sthankiya said he was enraged when he read a sign, on the opposing side, that said "Marijuana kills brain cells."

"This is disgusting, and more and more of this, over again, from people who haven't bothered to do 20 honest hours of research," he said.

Topher Graham and Tristan Risk, who were buying pot at the stand, said they took the day off work to celebrate legalization.

Graham said it means he won't have to buy pot from his friends anymore, while Risk said she sees legalization as a progressive step.

"I like that I can do it legally, safely and publicly. I don't have to feel like sneaky teenager anymore."

With files from Jon Hernandez