Not long ago, we were told that carbon taxes were unstoppable, and using Borg-like terms, resistance was futile. Well, that unstoppable part has taken a serious hit, and momentum is gathering to oppose Prime Minister Trudeau’s federal carbon price “backstop.”

In Ontario, Premier Doug Ford has moved to scrap the province’s cap-and-trade program. And has joined Saskatchewan in challenging federal authority in court. At a recent Council of the Federation meeting, Premier Ford and Saskatchewan Premier Scott Moe borrowed some language from the pipeline intransigent B.C. Premier John Horgan, saying “We will use every tool at our disposal” to rally opposition to the federally-imposed carbon tax.

Back east, Prince Edward Island and New Brunswick also reject the federal carbon-pricing plan. P.E.I. Environment Minister Richard Brown said the Island prefers its own greenhouse gas reduction plans to the federal tax, and that “We’re fighting for the Islanders here… if the federal government’s plan is to reduce carbon, we have a plan to reduce carbon.”

New Brunswick Environment Minister Serge Rousselle is “confident” that “when the moment comes to look at the New Brunswick plan, the federal government will see we’re meeting their requirements.”

Manitoba Premier Brian Pallister says the $50 federal carbon price would endanger the province’s economy and he’s willing to sue to preserve the flat $25/tonne he imposed this year.

Here in Alberta, the Notley government remains fully behind the carbon tax, but Jason Kenney, running under the UCP banner to become Alberta’s next premier, has promised to roll back the Alberta carbon tax and return to a previous regime that only taxed “major emitters.” He has also vowed to fight the federal price imposition by using some of Alberta’s carbon levy revenues to fight Ottawa in court.

Andrew Scheer, leader of the federal Conservative Party and challenger for Trudeau’s job in 2019, also opposes the federal price plan, insisting that the Tories will develop a plan to meet the Paris climate agreement commitment in other ways (currently unspecified). Whether that plan results in a lower price on carbon remains to be seen.

And yet, legal scholars suggest that the legal challenges will fail, as Ottawa has the authority to impose such taxes. But legal scholar Bryan Schwartz suggests the provinces may have a better case before the courts by insisting that their own carbon-pricing plans prevail.

Suddenly, a nationwide carbon tax doesn’t look quite so inevitable. Nor has it shown inevitability elsewhere in the world, despite supporters declaring the tax sacred. In 2014, Australia’s government under Tony Abbott repealed Australia’s carbon tax, saying the tax was “toxic” and hurt “ordinary people.”

The declaration of “inevitability” is primarily a tactic to persuade people not to challenge the tax. But where parliaments are concerned, little is graven in stone.

The question is not whether the federal government has the right to impose a federal carbon tax—it most likely does. The question is whether Prime Minister Trudeau, facing an election fight in 2019, will want to force the tax on the provinces when it could well be opposed by at least five premiers. That’s an optic the PM might want to avoid. Indeed, the inevitability of a national carbon tax in Canada suddenly seems significantly less inevitable.