The Act passed its final hurdle on Tuesday in a 52-29 vote in the Senate.
Once sales get up and running, Canada will become the first G7 industrialised country to have a legal nationwide cannabis market.
Justin Trudeau tweeted that because it's too easy for kids to buy weed, "criminals reap the profits".
Canada just legalized marijuana nationwide.
In the neighbouring U.S., nine states and the District of Columbia have legalised marijuana.
In the U.S., it is only allowed in the states of Colorado, Washington, Oregon, Alaska, California, Massachusetts, Maine and Nevada. "We're on the cusp of a sensible, responsible and equitable cannabis policy". "A fearless move on the part of the government", he said, according to CBC.
"With cannabis legislation, Canadians are ready for us to move forward", Harder told the Senate, predicting that "there may come a day, perhaps in the not-so-distant future, when we remember prohibition as absurd".
Many countries have decriminalised the use and possession of cannabis, abandoning prison sentences for consumers, but only a handful have gone as far as legalising its cultivation and use. We can start to be proactive in public education, ' he added.
"We have witnessed today a very historic vote that ends 90 years of prohibition, that's historic. These are good things for Canada".
But some health experts have anxious that the lower age will encourage use of a substance that can have long-term consequences on still-maturing brains.
Conservative senators remained resolutely opposed to legalization, however, and predicted passage of C-45 will not meet the government's objectives.
"I see a wall on the northern border", he said, adding that Canadians could face more scrutiny at the border if they admit to having smoked cannabis.