The threat of climate change is a national issue and the federal government has jurisdiction to impose a carbon price on some provinces under the “peace, order and good government” clause of Canada’s Constitution, lawyers for the Attorney-General argue in response to a Saskatchewan court challenge.

In a filing Tuesday, the government said federal action was needed to ensure that one province’s failure to act on climate change “does not adversely affect the nation as a whole,” and argued it gave ample opportunity for provinces to come up with their own plans that would be consistent with Canada’s international obligations. Saskatchewan is currently challenging the federal carbon-tax plan in its provincial court of appeal.

“GHG emissions are a matter of national concern,” the factum from the Attorney-General of Canada said. “Thus, Parliament has jurisdiction to legislate for the peace, order, and good government of Canada” under the Constitution Act of 1867.

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The response came as federal Conservative Leader Andrew Scheer and Ontario Premier Doug Ford met at Queen’s Park on Tuesday – a day after Mr. Ford played host to Saskatchewan Premier Scott Moe – to rally against the federal government’s climate plan. The response was also on the same day the Saskatchewan government introduced its own climate change law.

Open this photo in gallery Saskatchewan Premier Scott Moe, left, and Ontario Premier Doug Ford during a joint news conference in Toronto on Oct. 29, 2018. Christopher Katsarov/The Canadian Press

Mr. Scheer told reporters that conservatives across the country are aligned on the issue. “It’s quite clear that more and more voices provincially are fighting this job-killing carbon tax,” he said.

The federal leader brushed off suggestions that Mr. Ford is trying to become the dominant face of Conservatives in Canada. “There’s great co-operation between provincial and federal parties when we have interests of common ground," Mr. Scheer said.

Ontario has also challenged the federal carbon levy, and Ottawa’s response on that action will come later.

A spokesman for Mr. Moe said the Saskatchewan Ministry of Justice received the factum and its constitutional lawyers were analyzing it.

“However, we maintain that the carbon tax is unconstitutional because the federal government is applying a tax unevenly across the country based on their evaluation of provincial climate change plans, which they have no constitutional right to do,” spokesman Jim Billington said.

The Liberal government imposed its carbon pricing plan on four provinces – Saskatchewan, Manitoba, Ontario and New Brunswick – that did not meet the federal standard. It has two parts: a fuel tax to be paid by consumers and most businesses, and a large emitters’ levy that applies to a fraction of the emissions from industrial polluters. The fuel tax kicks in on April 1, starting at $20 a tonne – or roughly 4.5-cents a litre at the pump – and rising to $50 in 2022.

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Ottawa argued its carbon levy is a regulatory action intended to change behavior, not a tax enacted to raise revenue for federal coffers. To support that claim, it noted it will return all revenue from the levy back to the province in which it was raised – 90 per cent to households and the other 10 per cent to small and medium-sized business and the broader public sector.

Ontario Environment Minister Rod Phillips said this week that the province will have a climate plan that focuses on energy efficiency and financing low-carbon technology. However, Prime Minister Justin Trudeau has insisted that a carbon price must be part of any plan aimed at meeting emission-reduction commitments made under the Paris climate accord in 2015.

Editor’s note: (Oct. 31, 2018) An earlier version of this article incorrectly referred to the Constitution Act of 1967. It was 1867.

With files from The Canadian Press