Provincial and territorial premiers gathered in Whitehorse Thursday for their annual summer meeting are sending a shot across the bow of the federal government, ahead of this fall's First Ministers' meeting to finalize a national climate change strategy.

Their message: we'll meet your emissions reductions targets. Just don't tell us how to do it.

Saskatchewan Premier Brad Wall was only a few feet out of his vehicle Thursday morning before he began voicing his concerns over Prime Minister Justin Trudeau's comments yesterday in support of a carbon tax.

The question of exactly how Canada will meet emissions targets has been referred to a federal-provincial working group — a task that hasn't concluded yet.

Provinces say they went into the process with an understanding that different provinces would be allowed mechanisms of their own choosing: a carbon tax in B.C. or Alberta, for example, but a cap-and-trade scheme in Ontario and Quebec, or other proven ways to regulate elsewhere.

"This is a concern. Because if that's to be a legitimate process, where the premiers and the federal government work through some of these questions, why then is the prime minister and his... environment minister seemingly precluding the work of the committee?"

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"It seems as if the working group is unnecessary, they've already come to their decision: there's going to be some sort of national price for carbon that may or may not be that reflecting or respecting of the need for flexibility in the provinces."

Wall said his province has a price on carbon on a "de facto basis" because it "sells" the pollution for carbon capture and sequestration. That's his preferred way to respond to climate change.

Constitutional challenge?

Wall went a step farther in an interview later Thursday with CBC News Network's Power & Politics, saying he has already instructed provincial government lawyers to begin preparing for a constitutional challenge in the event the federal government acts unilaterally.

He suggested the case would be waged on the grounds that governments don't tax other governments.

Saskatchewan premier prepared to launch constitutional challenge to feds on carbon tax9:39

"We would constitutionally challenge any attempt by a federal government to impose a tax on, for example, a government Crown [corporation] like SaskPower or SaskEnergy," he told host Rosemary Barton. "This does not come in to play with the private sector, but it does with respect to government entities, we believe. And we would challenge it."

Noting that Canada is responsible for 1.6 per cent of global emissions, he said Canada should focus more on the global challenges, such as curbing emissions from coal plants, rather than hitting an already-reeling energy sector.

"Can you imagine, for example, in 2009 when the auto sector was reeling as a result of the great recession, if the country, the prime minister of the day, and the premiers were talking about a new tax on auto manufacturers?"

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Wall spoke to CBC News Network's Power & Politics during a break in the premiers meetings in Whitehorse Thursday. (Jonathan Hayward/Canadian Press)

Wall also said Trudeau's approach goes against his pledge for a "collaborative approach to federalism." 

'Made-in-the-South tax'

Wall is not alone in pushing back against Trudeau. The first press release reporters were handed on Thursday confirmed the three territorial governments are taking a "united stance" against a carbon tax.

"A carbon tax doesn't work in the North," it declared, calling it a "made-in-the-South" tax that would kill jobs, not create them, increasing the cost of living and undermining food security.

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Yukon Premier Darrell Pasloski reminded reporters Thursday that the climate change declaration out of the First Ministers meeting in Vancouver this spring talked about reflecting Canada's diversity and allowing provinces flexibility. (Jonathan Hayward/Canadian Press)

"Our resolve is strong," Yukon Premier Darrell Pasloski told reporters during a break in the talks. "We're not alone."

A carbon tax nationally would actually be a double tax for his territory, he says, because most goods are shipped from B.C., a jurisdiction that already has one.

'We already have a carbon tax'

Nova Scotia Premier Stephen McNeil, who also opposes a national carbon tax, said his province has worked diligently for several successive governments to cut emissions by 10 per cent compared to 1990, the only jurisdiction to meet and exceed this target through aggressive renewable energy plans and energy efficiency rebate programs.

"We already have a carbon tax — it's embedded in the cost of power. That's why we have some of the most expensive power in the country," he said.

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Nova Scotia Premier Stephen McNeil said his province already pays a form of a carbon tax: higher electricity rates, designed to recoup the cost of renewable energy initiatives and encourage efficient consumption. (Jonathan Hayward/Canadian Press)

"What the national government needs to do in my view is set a national target, and let the provinces achieve that how they best see fit."

The first communiqué issued by the premiers as a group "reiterated the importance of the federal government to respect areas of provincial jurisdiction."

"I'm confident that the federal government understands that each province and territory is going to need to do what they can — and I think the prime minister yesterday talked about the provinces doing what they need to do, in their way, to take part in a national plan," said Ontario Premier Kathleen Wynne.

"I think there's a strong recognition that we are all taking different actions. We all are committed to finding a way to meet those national targets," she said.

"We have a responsibility, at this table, to find a way to work together — each in our own way." 

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Ontario Premier Kathleen Wynne says her province has already taken a leadership role by shutting down its coal-fired electricity plants. (Jonathan Hayward/Canadian Press)

With files from Kathleen Harris