The U.S. Supreme Court heard arguments Tuesday, Dec. 10, over a proposed 88-mile railway that would transport tankers full of crude oil along the Colorado River.

The case, which includes Eagle County as a party, represents a challenge to how the National Environmental Policy Act is interpreted.

The railroad project was initially approved in 2021 by the Surface Transportation Board, which conducted a two-year environmental impact review, completing a 1,700-page statement under the National Environmental Policy Act.

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The proposed railway would connect oil fields in Utah to the Gulf Coast. Environmental groups have argued the railway could increase the risks of wildfires and oil spills into the Colorado River, a precious resource for Colorado and downriver communities. 

In 2022, Eagle County and five environmental groups sued to stop the construction of the railway. In 2023, it was halted by the U.S. Court of Appeals for the D.C. Circuit. Supporters of the railway appealed that decision, and the U.S. Supreme Court announced it would take up the question earlier this year.

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The railroad would use tracks along the Colorado River from Grand Junction to Winter Park and through Denver. 

In the arguments Tuesday, the justices delved deep into complex legal questions over how the law should be interpreted. At the heart of the arguments was whether the National Environmental Policy Act should only require consideration of a project’s “proximate effects” or possible further impacts. 

Some of the five conservative-leaning judges who heard arguments pushed back on the idea that the act should require projects to consider anything beyond those impacts. 

Justice Brett Kavanagh, who President Donald Trump appointed to the court in 2018, said the courts have taken an “overly aggressive role” in environmental cases. 

“It seems to me the problem that has crept in is conflating what the agency can do and should do from what the role of the courts is here,” he said. 

Chief Justice John Roberts, one of the more moderate judges appointed by a Republican president, questioned the limitations of the National Environmental Policy Act proposed by supporters of the railway, saying he had “trouble seeing how this is going to work out.” 

Some of the more liberal judges asked questions that implied an interest in keeping the National Environmental Policy Act purview broad.

When supporters of the railway explained how they think the National Environmental Policy Act should be limited to only “effects already remote in time or space,” Justice Sonia Sotomayor responded she didn’t know what that meant.

“You want absolute rules that make no sense,” she said. 

Judge Neil Gorsuch, who was also appointed by Trump, recused himself from the case after being pressured to do so because of his ties to the billionaire Philip Anschutz, who owns oil wells and could benefit if the project goes through.

While some speculation often comes from how justices frame and ask their questions, an official ruling in the case likely won’t be announced for weeks or months. Typically, the Supreme Court announces its rulings by the final day of its term in late June.