"We're doing it because we know it's not good for our children", Prime Minister Justin Trudeau said on the eve of the reform.
Ian Power, the first person to purchase recreational marijuana legally in Canada at the stroke of midnight said, "The stigma ends tonight, prohibition has ended right now".
Speaking of the law and how it may lead to young adult consuming more pot, Antonio Vigano, a medical marijuana specialist and research director at the Sante Cannabis clinic in Montreal, told the AFP: "As a doctor and as a father, I do not agree with the legalization of recreational cannabis".
Online cannabis customers will have to pay a $10 shipping fee, and any buyers who appear to be under 25 years old will be asked to prove they're of legal age when the drugs are delivered by Canada Post.
Cannabis use will be permitted in locations where smoking tobacco is permitted under the Smoke-Free Ontario Act, such as private homes and many outdoor public spaces like sidewalks.
Much of the paperwork needed for a blanket amnesty resides in local courthouses out of the immediate and easy reach of the federal government and the Parole Board, officials say. The brick-and-mortar stores would be privately-run.
"It's been hectic", said Roseanne Dampier, who joined her husband - both former welders - in opening Alternative Greens, a licensed store in Edmonton, Alberta. For instance, there are still some places in Canada where you can't smoke pot in public, and some provinces have outright banned growing it at home. A household can also grow only four plants and anything over the limit could attract hefty penalty.
As Canada welcomes legalization, supply shortages could develop, as happened in some USA states when legalization arrived.
The supply of recreational marijuana could be limited at least early on in some stores. California, the largest legal market in the US, earlier this month became the first state with a law mandating expungement of criminal convictions for marijuana-related offenses that no are longer illegal. Tobin, a longtime convenience store owner, said they will be cutting a ribbon and cake.
Meanwhile, industry players and watchers have said to expect product shortages at the outset. "You got to sell $250,000 worth of product in order to make $20,000".