Canada's Supreme Court ruled in favour of the federal government's carbon pricing policy on Thursday, upholding a central pillar of Prime Minister Justin's Trudeau's climate plan.
Noting that climate change is a threat to the country as a whole, the country's top court upheld the legality of the Greenhouse Gas Pollution Pricing Act, which had been challenged by the provinces of Alberta, Saskatchewan and Ontario.
"Parliament has jurisdiction to enact this law as a matter of national concern," Chief Justice Richard Wagner wrote in the ruling.
Carbon pricing, often called a carbon tax by opponents, is the lynchpin of Canada's plan to ultimately reach net-zero emissions by 2050. Ottawa will steadily ramp up the price of carbon to C$170 ($135.08) a ton by 2030, from C$30 a ton currently.
Under the carbon pricing act, Ottawa can impose a federal levy on provinces that do not have an adequate carbon pricing system of their own. Opposing provinces argued this infringed on their jurisdiction, but the Supreme Court ruled federal intervention was justified.
"All parties to this proceeding agree that climate change is an existential challenge. It is a threat of the highest order to the country, and indeed to the world," Wagner wrote.
The ruling was backed by six members of the nine-member court, with three dissenting opinions.
Canada is the fourth-largest oil producer in the world and the fifth-largest carbon emitter on a per capita basis.
The country needs to cut emissions by 30% below 2005 levels by 2030 to fulfil its international climate commitments, which would involve slashing annual emissions to 511 megatons, compared with 729 megatons in 2018.
The Liberal government unveiled a strengthened climate plan last year aimed at reducing emissions to 503 megatons.
"Carbon pricing is the central defining feature of their climate strategy," said Sarah Petrevan, policy director at think tank Clean Energy Canada.
($1 = 1.2585 Canadian dollars)