BILLINGS, Mont. (AP) — Environmentalists and Native Americans can proceed with lawsuits challenging President Donald Trump’s approval of the Keystone XL oil pipeline from Canada, a federal judge in Montana ruled Friday.

U.S. District Judge Brian Morris expressed skepticism over government arguments that Trump has unilateral authority to approve the $8 billion pipeline. In a separate ruling, the judge said the Rosebud Sioux and Fort Belknap Indian tribes had valid claims that approval of the line violated their treaty rights.

But Morris denied a request from environmentalists to impose a court injunction blocking preliminary work on the pipeline, since no such work is planned until spring 2020.

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Morris had blocked work on the line in 2018, prompting Trump to issue a new permit in March in an attempt to circumvent the courts.

The 1,200-mile (1,930-kilometer) pipeline would transport up to 830,000 barrels (35 million gallons) of crude daily from western Canada to terminals on the Gulf Coast.

Opponents worry burning the tar sands oil that will be carried by the line will make climate change worse, and that it could break and spill into water bodies such as Montana’s Missouri River.

TC Energy of Canada first proposed the project more than a decade ago but has been unable to get past the numerous lawsuits against it. Trump has been a strong supporter and revived Keystone XL after it was rejected under President Barack Obama.