OTTAWA, Ontario — The Supreme Court of Canada ruled Thursday that Prime Minister Justin Trudeau's national carbon price is entirely constitutional.

The decision upholds a pivotal part of Trudeau's climate change plan. In 2019, the federal government set a minimum price on carbon emissions in provinces which don't have an equivalent provincial price, a law that was challenged by the oil-rich province of Alberta as well as conservative governments in Saskatchewan and Ontario.

Chief Justice Richard Wagner said in the written ruling that climate change is a real and existential threat to Canada and the entire world, and evidence shows a price on pollution is a critical element to addressing it.

"The undisputed existence of a threat to the future of humanity cannot be ignored," he wrote.

Wagner also said the Canadian provinces can't set minimum national prices on their own and if even one province fails to reduce their emissions it could have an inordinate impact on the rest of the country.

It is a split decision with six judges entirely in favor, one partial dissent and two entirely in disagreement with the majority.

Federal Environment Minister Jonathan Wilkinson issued an immediate statement lauding the decision as "a win for the millions of Canadians who believe we must build a prosperous economy that fights climate change."

The program applies a price to fuel purchases by individuals and businesses with lower emissions, and on part of the actual emissions produced by entities with large emissions, such as pipelines, manufacturing plants and coal-fired power plants.