Open this photo in gallery Saskatchewan Premier Scott Moe speaks at the Legislative Building in Regina this month. Mark Taylor/The Canadian Press

Saskatchewan is showing no sign of backing down from being a thorn in Ottawa’s side when it comes to climate policy, and has formally launched a constitutional reference case to challenge the federal government’s ability to force a carbon tax on the provinces.

In a case that could make its way to the Supreme Court of Canada, the province asked the Saskatchewan Court of Appeal Wednesday whether a carbon price as laid out in Ottawa’s budget implementation bill last month would be “unconstitutional, in whole or in part.” Premier Scott Moe said the federal Liberals have unfairly made themselves “judge and jury” to decide which provincial climate plans they favour.

“It fails to respect the sovereignty and the autonomy of the provinces with respect to matters under their jurisdiction,” Mr. Moe said in an interview. “Saskatchewan should not be subject to this tax simply because the Trudeau Liberals do not like our climate-change plan.”

Story continues below advertisement

The move raises the stakes in a long-simmering provincial-federal battle over carbon pricing, with Saskatchewan standing as a key objector to Ottawa’s plans for a pan-Canadian climate-change framework. New Brunswick is another potential holdout to the plan, and Manitoba has said it will take Ottawa to court if it imposes a higher carbon tax than the province wants. With provincial elections looming in Ontario and Alberta, leading conservative opposition leaders in those provinces are seizing on voter disenchantment with the federal Liberal climate plan.

Setting the stage for a much broader national battle, Ontario Progressive Conservative Leader Doug Ford said late Wednesday he would support Saskatchewan’s reference case, adding “the people of Ontario can’t afford a carbon tax in whatever name or form. Not now. Not ever.”

Alberta opposition leader Jason Kenney announced his own United Conservative Party will seek intervenor status to support Saskatchewan, saying more provinces are likely to join in. “The wind has shifted on this issue.”

However, federal Environment Minister Catherine McKenna said it’s clear Ottawa has the legal authority to implement a carbon price.

“We are disappointed to see this news because we’re all in this together. We’re in it together to tackle climate change and take advantage of the $30-trillion opportunity of the clean economy,” Ms. McKenna said. “The government of Manitoba sought a legal opinion – they realized the federal governments had jurisdiction.”

Last year, Manitoba’s Conservative government obtained a legal opinion that concluded Ottawa has the right to impose a carbon tax on provinces that do not adopt their own. However, the province would likely win a legal contest if Ottawa tried to impose an additional levy on a provincial one, the legal opinion said.

The crux of Saskatchewan’s argument focuses on the leeway Ottawa has given provinces in the implementation of their plans. The federal government has demanded all provinces adopt a carbon price of $10 per tonne this year, with the price increasing by $10 each year until it hits $50 in 2022. Provinces such as British Columbia and Alberta have established an actual carbon tax, while Ottawa has said that Ontario and Quebec’s cap-and-trade systems will result in equivalent reductions in greenhouse gas emissions.

Story continues below advertisement

Critics of Saskatchewan’s climate plan say it falls short, with a lack of specific targets and detailed implementation plans. Ms. McKenna has said that, if Saskatchewan doesn’t change course, her government will use its “backstop” to ensure that a carbon price is applied.

But Mr. Moe said Saskatchewan is being unfairly penalized for taking a different path. The province’s plan − introduced under former premier Brad Wall − includes developing sector-specific emissions standards, and doubling renewable power to 50 per cent of SaskPower’s generating capacity by 2030. Mr. Moe said Saskatchewan’s uranium exports are used to generate emission-free nuclear power in Asia, and should be counted by Ottawa.

A carbon tax, he said, will make his province’s oil and gas, agriculture, mining and transportation sectors less competitive. “We’re having the wrong conversation in this nation – we’re having a conversation about how we can best tax our industries, as opposed to having a conversation about how we can actually reduce emissions.”

University of Alberta law professor Eric Adams said Saskatchewan faces an uphill battle, as a balance of legal opinion suggests Ottawa will be successful in defending its legislation. Saskatchewan is “making a somewhat novel argument on the basis of underlying federal principles.”