A federal appeals court ordered work to stop at a major oil project on Alaska’s North Slope, siding with conservation and Indigenous groups.

The decision Saturday by the 9th U.S. Circuit Court of Appeals will stop on-the-ground work for the winter at the Willow project operated by ConocoPhillips Co., the Anchorage Daily News reported Sunday.

Ice roads support wintertime work at projects on Alaska’s North Slope, but they melt in the spring and that drastically reduces what can be done for all but a handful of months.

The Willow project in the National Petroleum Reserve-Alaska was expected to provide jobs for about 120 people this year.

Sovereign Inupiat for a Living Arctic, the Center for Biological Diversity, Friends of the Earth and other groups sued last fall to stop the project altogether, not just in winter. They argue that the Trump administration didn’t follow environmental laws before approving the project.

This month, the groups asked the 9th Circuit to overturn a U.S. District Court decision to allow winter work to continue. After the groups appealed, short-term work was halted.

Ninth Circuit Judges William Canby and Michelle Friedland agreed that the plaintiffs would be harmed without an injunction that stops the work until the court can rule on the case itself.

ConocoPhillips spokeswoman Natalie Lowman didn’t say in an email Sunday whether the company plans to appeal the work stoppage.