MONTREAL—Prime Minister Justin Trudeau’s government has been on a legal roll this month.

Over the space of the last few weeks, it has secured essential court victories for both its carbon tax and its pipeline plans.

But the Liberals would be best to hold the champagne. Those wins could yet come at a cost on the campaign trail as opponents of the carbon tax and the Trans Mountain pipeline respectively regroup on the electoral front.

On Friday, the British Columbia Court of Appeal found that the province does not have the constitutional right to limit the flow of bitumen oil that transits through its territory.

Had B.C.’s top court found the opposite, the expansion of the Trans Mountain pipeline would have been in jeopardy. And that might have been just one of the consequences of a ruling favourable to the province’s intentions.

Inasmuch as what is constitutionally good for the goose is good for the gander, the Quebec government would almost certainly have come under pressure from its own environmental lobby to adopt regulations similar to those B.C. was contemplating.

Access to markets for Alberta’s bitumen oil would have become even more problematic.

And while the Supreme Court would still have had the last say on the issue, closure on that front would not have been forthcoming before the next federal campaign.

Between now and then, B.C. and Alberta would more than ever have been at each other’s throats with Trudeau very much caught in the crossfire.

The prime minister may have dodged that bullet on Friday. The ruling may even result in a drop in the political temperature between the two westernmost provinces.

On his way to winning the last B.C. election, NDP premier John Horgan had promised to use every tool at the government’s disposal to stop the pipeline expansion.

But after losing the court reference, Horgan may be looking at an empty tool box. B.C. will appeal the ruling to the Supreme Court. But given that the decision is unanimous, a reversal may be a long shot.

Earlier this month a majority on the Saskatchewan Court of Appeal agreed the federal carbon tax is constitutional. That is hardly the definitive word of the courts on the issue. That ruling will be appealed to the Supreme Court. Similar cases are winding their way to the top court in Ontario, Manitoba and, soon, Alberta.

In the immediate though, the upside for Trudeau is that the constitutionality of both main components of the climate change/energy strategy he has been pursuing since he was in power has been validated in time for the upcoming election.

Here is the political downside.

On the pipeline front, the B.C. ruling removes the most plausible reason for keeping the Trans Mountain expansion on hold beyond next month. The federal cabinet’s latest deadline for deciding whether to give the project the green light is June 18.

There have been calls for the prime minister to keep his finger on the pause button at least until after the election.

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The imminence of the federal campaign, the unpopularity of the expansion in B.C., that province’s weight in the Liberals’ election fortunes all loom large in the calculations behind the notion of keeping Trans Mountain on hold.

But the case for shovelling the decision forward was always more political than substantial.

Alberta’s withdrawal — under its new Conservative government — from the national climate change framework does not in itself provide a solid rationale for further delaying the expansion, not when the federal government is about to replace the tax the province is eliminating with a federal levy.

Friday’s court ruling has deprived those who would have Trudeau sit on the Trans Mountain file until after the election of much needed ammunition.

That being said, in the wake of the two court rulings, opponents of both the pipeline expansion and the federal carbon tax are poised not to lay down their weapons but to take their fight to the federal electoral battlefield.

On Trans Mountain, expect the Green party and the New Democrats to argue that the larger their caucuses in the next Parliament, the greater the odds of a minority government on which the anti-pipeline forces would have leverage.

On the carbon tax, Conservative strategists, even as they publicly mourned the Saskatchewan ruling, were probably not all that unhappy with the defeat of the province’s challenge.

For one, it was a split decision — a result that shored up the contention of carbon tax opponents that their court challenges are not frivolous.

More importantly, the Saskatchewan ruling is bound to help the federal Conservative party drive home the message that the federal ballot box offers those who would see the carbon tax eliminated the surest and quickest path to achieving that end.

On carbon pricing and on pipelines, Trudeau’s legal hand has been strengthened this month. But so have the electoral hands of his rivals.

Chantal Hébert is a columnist based in Ottawa covering politics. Follow her on Twitter: @ChantalHbert

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