The court released its order on Monday on who would be granted the special status.
The federal government argued in a brief submitted to the court the UCP should not be an intervenor because it would be “political and speculative.”
It also said it should reject an affidavit from the CTF because it “has not established any special expertise in general economics or the economics of carbon pricing.”
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A number of other groups were granted intervenor status, including the David Suzuki Foundation and the Assembly of First Nations. A complete list follows at the end of this story.
SaskPower and SaskEnergy, along with the British Columbia government and a coalition headed by Climate Justice Saskatoon, have also been granted leave to file additional materials they would like added to the record.
They have until Dec. 18 to serve the material and file it with the court.
The governments of Saskatchewan and Canada will have three days to respond.
Saskatchewan filed the constitutional challenge against the Greenhouse Gas Pollution Pricing Act, saying the federal government does not have the authority to impose a carbon price on the provinces.
Saskatchewan had been joined by the governments of Ontario, Manitoba, and New Brunswick in opposition to the federal carbon pricing plan.
Ottawa plans on imposing a carbon tax in January on jurisdictions that don’t have a climate plan that meets its standards.
The Saskatchewan case is expected to be heard starting on Feb. 13. Ontario’s challenge is expected to be heard by that province’s appeal court in April 2019.
With files from David Akin