The U.S. Supreme Court on Thursday backed a multibillion-dollar oil railroad expansion in Utah that faced fierce opposition from Colorado communities that fear the project could cause an environmental disaster as it enables the transport of tens of millions more gallons of crude oil across the state and along the Colorado River.

The high court’s 8-0 opinion reversed a prior decision by an appeals court that found a government agency violated the country’s bedrock environmental law — the National Environmental Policy Act — by failing to analyze potential environmental impacts of the Uinta Basin Railway outside of the immediate area of the proposed railway, like in Colorado.

The 88-mile railway expansion would connect oil and gas producers in Utah’s Uinta Basin to the existing rail system and greatly increase the amount of crude oil transported across Colorado to refineries on the Gulf Coast.

Plaintiffs in the litigation — led by Colorado’s Eagle County — argued that the U.S. Surface Transportation Board failed to consider in its environmental review how the railway could impact land, water and air away from the immediate construction site.

They argued increased train traffic raised the risk of wildfires along the railway and increased the chance of a spill of crude oil into the Colorado River, which provides water for a region of 40 million people.

“We’re very disappointed with the decision,” said attorney Nathaniel Hunt, who represented Eagle County in the case. “Overall, it kind of rocks the environmental world.”Colorado Attorney General Phil Weiser and a dozen local governments in Colorado filed briefs in the case, urging the Supreme Court to leave the lower court’s decision in place.

“Today, the U.S. Supreme Court overturned the lower court’s decision to block a risky scheme to transport waxy crude oil along the Colorado River, right alongside our most critical water resource and posing major risks to Colorado’s Western Slope communities,” Weiser said Thursday in a statement. “The court’s opinion allows agencies to ignore the upstream and downstream environmental harms of projects.”

U.S. Rep. Diana DeGette, a Denver Democrat, said the court’s decision “lays the groundwork for environmental catastrophe.”

“Increasing fracking levels and transporting them across the country would not only harm the communities through which the train travels, including those in Denver, but it would further devastate the communities surrounding the facilities where this oil would burn,” she said in a statement.

The justices found that regulators were right to consider only the direct, local effects of the project, rather than the wider upstream and downstream impacts. Justice Brett Kavanaugh wrote that courts should defer to regulators on “where to draw the line” on what factors to take into account while analyzing projects’ environmental impacts under the National Environmental Policy Act.

“Simply stated, NEPA is a procedural cross-check, not a substantive roadblock,” he wrote of the policy act reviews. “The goal of the law is to inform agency decision making, not to paralyze it.”

Four other conservative justices joined his opinion, and three liberal justices wrote their own opinion, which reached the same conclusion but through different reasoning. Justice Neil Gorsuch recused himself from the case after ethics watchdogs noted his ties to Colorado billionaire Philip Anschutz, whose companies could profit if the railway is built. Gorsuch, as a lawyer in private practice, previously represented Anschutz.

The justices remanded the case back to the lower court, which now will reconsider the issues through the lens of the court’s decision.

The Supreme Court did not rule on other issues that Eagle County and other plaintiffs won in the lower court, Hunt said. The plaintiffs will continue to fight the railway expansion when it returns to the U.S. Court of Appeals for the D.C. Circuit.

“We don’t think this changes things,” he said. “We look forward to going back to the D.C. Circuit.”

Environmental groups said the decision would have sweeping impacts on National Environmental Policy Act reviews and limit the scope of environmental reviews required by the law.

“As noted, the biggest project beneficiaries of this decision will likely be large energy, natural resource, infrastructure and transportation projects,” said Michael Drysdale, an environmental attorney with Dorsey and Whitney.

“This is because these types of projects tend to generate a lot of upstream and downstream environmental effects, spur or involve numerous related but separate projects, and generate intense opposition. This has, for decades, made permitting such projects very challenging under NEPA. It may now be easier at the federal level, if not truly simple.”

The court’s conservative majority has taken steps to curtail the power of federal regulators in other cases, including striking down the decades-old Chevron doctrine that made it easier for the federal government to set a wide range of regulations.

The ruling comes after President Donald Trump’s vow to boost U.S. oil and gas drilling and move away from former President Joe Biden’s focus on climate change. The administration announced last month it’s speeding up environmental reviews of projects required under the same law at the center of the Utah case, compressing a process that typically takes a year or more into just weeks.

“The court’s decision gives agencies a green light to ignore the reasonably foreseeable consequences of their decisions and avoid confronting them,” said Sambhav Sankar, senior vice president of programs at Earthjustice.

Wendy Park, a senior attorney at the Center for Biological Diversity, said opponents would continue to fight the Utah project. “

This disastrous decision to undermine our nation’s bedrock environmental law means our air and water will be more polluted, the climate and extinction crises will intensify, and people will be less healthy,” she said.

The project’s public partner applauded the ruling. “It represents a turning point for rural Utah — bringing safer, sustainable, more efficient transportation options, and opening new doors for investment and economic stability,” said Keith Heaton, director of the Seven County Infrastructure Coalition.