The country's highest court will deliver a decision today on the fate of the federal price on pollution.
The Supreme Court ruling could become a landmark case for the division of federal and provincial powers.
The court will decide whether the Trudeau Liberals' Greenhouse Gas Pollution Pricing Act is constitutional.
Passed in 2018, the act imposes a minimum price on greenhouse gas emissions in provinces that don't have an equivalent system of their own.
Alberta, Saskatchewan and Ontario have all challenged the law in court, saying it infringes on their taxing powers and their right to develop their own natural resources.