The climate impact of Alberta’s tar sands/oil sands production is the “deal-breaker” that should stop Kinder Morgan’s Trans Mountain pipeline expansion in its tracks, writes Toronto Star National Affairs Columnist Tom Walkom.

Starting from the perspective that the project “has law, economics, and the Constitution on its side,” Walkom concludes in a column last week that “that one thing—the danger posed by climate change—is the deal-breaker that could and should kill this project. It trumps everything else.”

While a bigger pipeline wouldn’t increase Canada’s greenhouse gas emissions on its own, “it would support Alberta’s troubled oilsands industry, which does,” he writes. “While the oilsands accounted for just under 10% of Canada’s greenhouse gases in 2014, they are the fastest-growing source of carbon emissions in the country. In climate terms, the most sensible course of action would be to gradually shut the oilsands down. Thanks to the growth of cheaper forms of energy, they are already headed in that direction. It wouldn’t take much of a nudge to finish the job.”

Except that “both the New Democratic Party government in Alberta and the Liberal government in Ottawa have been trying to have it both ways,” Walkom contends. “On the one hand, they’ve put in place measures to reduce emissions marginally. On the other, they have been pushing pipelines, like Kinder Morgan’s Trans Mountain conduit, that would encourage expanded oilsands production and thus more emissions. Prime Minister Justin Trudeau says this shows that fighting climate change need not threaten economic growth. What it really shows is that half measures get you only halfway.”

If the Kinder Morgan frenzy is settled by the letter of the law, “pipeline proponents have the edge,” he concludes. “But anti-pipeline protestors have already shown they are willing to face arrest to make their point. If this becomes a showdown over the future of the planet, law may not be enough.”