'Greatest existential threat of our time': Ottawa makes carbon tax case in court

The climate crisis is a national and global issue that can't be fought entirely by the provinces, a lawyer for the federal government argued Tuesday.

"The context of this case is the greatest existential threat of our time," said Sharlene Telles-Langdon in her opening arguments in support of Ottawa's carbon tax.

The law that brought in the tax is being challenged this week by Alberta in the province's Court of Appeal.

Ontario and Saskatchewan have also gone to their top courts to oppose the tax, but lost. They are appealing to the Supreme Court of Canada.

Ottawa argues its authority for the tax comes from the Constitution's peace, order and good government clause. Establishing minimum national standards on greenhouse gas emissions "is a matter of national concern that only Parliament can address."

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Telles-Langdon argued in court that the circumstances surrounding climate change have developed enough to make it a national concern. Much more is known about it, she said, and the severity of the threat has greatly increased.

"There has been a constitutionally important transformation," she said. "We're now in a situation where the dimensions of the problem are international and global."

The carbon tax flows from the federal government's right to sign international treaties, she added, and is part of living up to climate change accords such as the Paris Agreement.

"The treaties matter," Telles-Langdon said.

She told the five-judge panel that the carbon tax grew out of co-operation between the federal government and the provinces that began in 2016 after a first ministers meeting in Vancouver. The provinces agreed at that time that carbon pricing shouldn't make businesses in one province less competitive in comparison with others.

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Several provinces already had carbon-pricing schemes at that time, she said.

"When this was signed, part of the agreement was that other provinces be brought on board."

She argued that the tax still gives provinces the flexibility to meet a minimum standard in their own way. She pointed to Alberta's recently approved levy on industrial emitters.

The federal lawyer faced repeated questions from judges about the scope of the legislation and how it would be implemented. In response to a question on whether Ottawa could simply ignore competitive pressures on Canadian businesses, Telles-Langdon pleaded with the court "to be reasonable about what Parliament does."

"The federal government has to be very cognizant of the economy of the country as a whole."

In Calgary, federal Environment Minister Jonathan Wilkinson said the Liberal government believes the tax will stand.

"The federal government remains confident that our arguments are very much valid and that we are well within our constitutional parameters to ensure that pollution from coast to coast to coast is priced.

"We fully expect to prevail in the Supreme Court."

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On Monday, a lawyer for the Alberta government argued that allowing the tax law to stand would give the federal government a tool it could use to repeatedly chip away at provincial powers.

Peter Gall said issues of "national concern" are rare. Greenhouse gases don't meet the test, he said, and upholding the tax law would open the door to Parliament stepping into provincial matters whenever it wanted.

Lawyers for attorneys-general in Ontario and Saskatchewan have already presented arguments in support of Alberta's challenge.

Those representing New Brunswick and British Columbia are also to speak during the hearing. Eight First Nations, non-governmental groups and Crown corporations have been granted intervener status as well.