Judge Brian Morris, a US District Judge for the District of Montana, canceled a key permit for the Keystone XL oil pipeline on Wednesday.

In 2017 the US Army Corps of Engineers (Corps) reissued Nationwide Permit 12. The permit authorizes “discharges of dredged of fill material into jurisdictional waters” and is necessary for the water-crossings of the Keystone XL pipeline.

Morris found substantial evidence that reissuing the permit “may affect” certain endangered species, such as the pallid sturgeon and the American burying beetle.

Under the Endangered Species Act, an agency must undergo a formal consultation with the US Fish and Wildlife Service for any activity that “may affect” endangered species. The Corps failed to initiate this consultation when it reissued the permit in 2017.

Because the Corps violated the Endangered Species Act, Morris vacated the permit and enjoined the Corps from authorizing any dredge or fill activities until the completion of the consultation process and compliance with its biological opinion.

This ruling occurred less than two weeks after the long-debated project had finally begun. While the ruling will not stop the work that has begun along the US-Canada border, it could seriously delay the project. The permit will be needed for future construction across hundreds of rivers and streams between the Canadian border and Nebraska.