The province is taking the next step in its legal fight against the carbon tax.

Premier Scott Moe says the province filed an appeal with the Supreme Court of Canada late Thursday afternoon. Moe made the announcement in a speech to supporters at a dinner in Saskatoon.

Earlier this month, in a three-two decision, the Saskatchewan Court of Appeal ruled against the province in its appeal of the federal carbon pricing plan.

Saskatchewan had asked the court to rule on whether a federal carbon tax is constitutional.

The province said the levy is unconstitutional as it would not be applied evenly across all jurisdictions. Saskatchewan has argued that Ottawa has “no authority to second-guess provincial decisions,” and believes its own emissions pricing plan is acceptable.

Legal experts have noted the fact that the courts haven’t yet experienced climate change as the specific context for a constitutional issue.

Ottawa says it has the power to impose a carbon price on provinces because Section 91 of the constitution says it can pass laws “for peace, order and good government of Canada.” A lawyer for the federal government said this power can be asserted because climate change is a matter of national concern.

Minister of Justice Don Morgan says the case is heading into unique legal waters.

"We are going into areas of law that have not been well canvassed by our courts.  So we think it's an important national issue."