Saskatchewan's highest court is set to release its decision Friday in a court case that has pitted the province against the federal government.

The case involves the federal carbon tax the Trudeau government imposed on Saskatchewan and several other provinces on April 1.

In February, lawyers for Saskatchewan argued in the Court of Appeal in Regina that the tax is unfair and unconstitutional.

The quick turnaround on the decision shows the court prioritized the decision, said Dwight Newman, a constitutional law expert and professor at the University of Saskatchewan.

Newman said it's important to note that the ruling doesn't weigh in on the best policy for tackling climate change, nor the merits of a carbon tax.

Constitutional law expert Dwight Newman said the Supreme Court might not hear the decision if all provincial courts of appeal reach the same conclusion. (Dwight Newman)

"This is a court ruling on the law under the Constitution," he said.

Newman said the court's decision will affect more than just national environmental policy; it will also affect how much power the federal government has over matters of national concern.

"It's a significant precedent."

This ruling will decide whether the federal government has the power to regulate carbon emissions that cause climate change, said Stewart Elgie, a professor at the University of Ottawa and an expert in constitutional and environmental law.

Elgie was a consultant for Canada's Ecofiscal Commission, which appeared as an intervenor in the Saskatchewan court case. It argued that the federal and provincial governments should share authority over carbon pricing — with the federal government setting national minimum standards and provinces tweaking policy within that, once they meet those standards, Elgie said.

"Interestingly, neither Saskatchewan nor Ontario is challenging the fact that carbon pricing is the lowest-cost way to reduce emissions," he said.

"They're simply arguing the federal government can't do it."

Elgie said the federal government argued that emissions and climate change are global in scope, and thus cross provincial and national borders.

"So the federal government has authority to set national standards, the same way they do with health care and other issues," he said of its argument.

"Saskatchewan is arguing that climate change is a local issue, so they have exclusive authority over it."

Case could end up at Supreme Court of Canada

Experts agree the case will likely be decided in the Supreme Court of Canada. Newman said it's a "matter of constitutional significance nationally," and whichever side is on the losing end of Friday's decision will probably appeal.

Under the Supreme Court Act, provinces have an automatic right of appeal for provincial reference opinion. Therefore the Supreme Court of Canada cannot refuse to hear an appeal if the province submits one.

University of Ottawa professor Stewart Elgie says the Saskatchewan decision is important, but it doesn't mean the carbon tax will be put on hold. (Stewart Elgie/uOttawa)

The matter is making its way through the courts in other provinces, as well.

Earlier this month, the province of Ontario had a similar hearing. Ontario argued that the federal carbon tax was unconstitutional. Manitoba announced in early April it would be launching an appeals-court challenge of its own.

Newman said Saskatchewan's decision will be considered a "persuasive authority" in other provinces. That means other courts can reference the judgment, but they will ultimately make their own decisions.

Elgie noted that the Saskatchewan decision is important, but said it's not the end of the process and it doesn't mean the carbon tax will be put on hold.

"Whatever it decides, the federal carbon-pricing law will still stand, and we won't know the final answer probably until early 2020, when the Supreme Court rules on it," he said.

"Then we'll know for sure whether or not carbon pricing is constitutional."

The court will rule on the law, but Elgie said an underlying question will remain.

"Behind the legal issues, the real question is whether Canada will take meaningful action on climate change," he said. "Are we finally going to act on climate change, or will we pass this problem on to our kids?"

Farmers' concerns

Margaret Hansen, who farms near Moose Jaw, Sask., says she has a 'pit in [her] stomach' from anticipating extra costs due to the federal carbon tax. (submitted)

Margaret Hansen, who farms near Moose Jaw and is the Saskatchewan vice-president of the Western Canadian Wheat Growers Association, said she's keenly waiting for the court's decision.

"We're just putting the crop in the ground, and it's been awhile since I've had such a pit in my stomach about putting a crop in the ground," she said.

Hansen said she's concerned about extra costs, and worries she'll have trouble competing with places that don't have a carbon tax.

Although farm fuel is exempt from the tax, she said she expects to pay more for nearly everything else, including fertilizer and machinery. Hansen said farmers are already working to reduce emissions, and she "can't see how the tax will cause any [more] change in behaviour."