Canada’s top court on Friday upheld a Quebec ban on homegrown cannabis that critics charged was at odds with federal legalization of pot that allows a few plants to be grown for personal use.

The unanimous decision effectively maintains a Quebec government monopoly on cannabis sales within the province.

“In pursuing public health and security objectives, the Quebec legislature has jurisdiction to prohibit the possession and cultivation of cannabis (at home) for personal purposes,” said a court summary of the ruling.

Chief Justice Richard Wagner wrote in the decision itself that the prohibition was “a means of steering consumers to the only source of supply considered to be reliable and safe.”

This, he said, ensures “control of the quality of the products offered, education on the risks of cannabis consumption and compliance with rules on the minimum age for purchasing cannabis,” among other things.

He also said both federal law and the Quebec ban share the same objective, which is to undercut and eventually displace a cannabis black market.

Canada became only the second nation to legalize recreational cannabis, after Uruguay, in October 2018, giving birth to a new cultivation and retail industry.

The federal law permitted also the possession and cultivation of up to four cannabis plants for personal use. Ottawa left it up to the provinces, however, to regulate practical matters such as how pot can be stored and sold.

A patchwork of public and private online portals and bricks and mortar stores popped up across the country, as each province rolled out their own marijuana retailing framework.

Quebec chose to make cannabis available to consumers only through government stores.

A local resident first brought the case before the courts in 2019, arguing through his lawyer that the ban on homegrown cannabis contradicted the federal law.

A lower court ruled that the prohibition was unconstitutional, but that was overturned on appeal before the Supreme Court weighed in.