TORONTO (AP) — Canada's Federal Court of Appeal has quashed the approval of the contentious Trans Mountain pipeline expansion that would nearly triple the flow of oil from the Alberta oil sands to the Pacific Coast.

Thursday's decision means the country's National Energy Board will have to redo its review of the pipeline. Prime Minister Justin Trudeau's government approved Trans Mountain in 2016 and was so determined to see it built that it announced plans this spring to buy the pipeline.

It faces stiff environmental opposition from British Columbia's provincial government and activists. Houston-based Kinder Morgan earlier halted essential spending on the project and said it would cancel it altogether if the national and provincial governments could not guarantee it.

The pipeline would allow Canada to diversify and vastly increase exports to Asia.