LINCOLN, Neb.—Opponents of TransCanada Corp.’s (NYSE: TRP) proposed Keystone XL pipeline appealed a decision by Nebraska regulators to approve a path for the project through the state, a lawyer for the opponents said on Jan. 5.

The legal challenge throws up another obstacle to the long-delayed project, which environmentalists have made a symbol of their fight against climate change but which President Donald Trump supports as a job creator.

The Nebraska Public Service Commission in November approved a route for Keystone XL, lifting what appeared to be the last big regulatory hurdle for the 1,179-mile pipeline linking the oil fields of Canada’s Alberta province to U.S. refineries, initially proposed nearly a decade ago.

But the approval was not for TransCanada’s preferred path, and was instead for an alternative route that shifted it eastward to an existing pipeline right-of-way.

Lawyers for opponents of the pipeline—which include landowners along the route—have argued that the commission was not permitted to approve anything but the original route TransCanada had requested in its application.

Attorney David Domina told Reuters on Jan. 5 that TransCanada’s approval was for a “route not supported by an application. ... So we appealed.” The appeal was filed on Dec. 29.

A TransCanada official declined to comment.

The proposed pipeline has been a lightning rod of controversy for nearly a decade, pitting environmentalists worried about spills and global warming against business advocates who say the project will lower fuel prices, shore up national security and bring jobs.

The Trump administration granted TransCanada a federal permit for the pipeline in March, reversing a decision by former President Barack Obama to reject the project on environmental grounds. That left Nebraska—the only one of three states that had not approved a route for the line—as the final hurdle.

TransCanada has said it expects enough commercial support to make the project viable, though it has not made a final investment decision.