SIOUX FALLS, S.D. (AP) — Foes of the Keystone XL oil pipeline said Friday they may appeal a South Dakota judge's decision upholding state regulators' approval for the pipeline to cross the state, potentially extending the legal conflict over the pipeline.

Two groups said they are weighing whether to raise the issue to the state Supreme Court, while an attorney for a Native American tribe in South Dakota also said its lawyers are examining an appeal. A state judge last month affirmed a Public Utilities Commission decision that tribes, landowners and others challenged.

Robin Martinez, an attorney for conservation and family agriculture group Dakota Rural Action, called the judge's decision a "disappointment." The organization is considering an appeal, director Frank James said.

"The clear effect is on the landowners who are now living with this perpetual threat of having their land taken away from them for this pipeline that may or may not ever happen," Martinez said. "That's a heavy burden."

The Keystone XL project would move crude oil from Alberta, Canada, across Montana and South Dakota to Nebraska, where it would connect with existing pipelines feeding refineries along the Gulf Coast.

Terry Cunha, a spokesman for pipeline developer TransCanada Corp., praised the decision in a statement, saying the project will help U.S. energy security, create well-paying jobs and offer substantial economic benefits. Native American tribes, some landowners and environmental groups oppose the pipeline, fearing it would contaminate water supplies and contribute to pollution.

The Public Utilities Commission initially authorized TransCanada's project in 2010, but the permit had to be revisited because construction didn't start within the required four years. The panel last year voted to accept TransCanada's guarantee that it would meet all conditions laid out by the commission when it first approved that state's portion of the project.

Opponents appealed the commission's decision to state court, which heard arguments in March. Judge John Brown wrote in his decision that the issues opponents raised have been adequately addressed by the commission or aren't appropriate to be addressed in the case.

The pipeline has frequently been delayed. Former President Barack Obama rejected the project in 2015, but President Donald Trump's administration overturned that decision this year. Nebraska regulators haven't decided whether to approve the proposed route through that state.