Editor's note: This story was produced by the Sierra Nevada Ally, a nonprofit, nonpartisan news outlet focused on civics, climate and culture.

In a landmark decision, the Supreme Court in June voted to abolish the longstanding ruling known as the “Chevron deference.” This decision, in place for four decades, was instrumental in helping courts make challenging legal decisions with sound, science-based information and facts, often from the agencies involved. Without it, courts can make decisions based on politics over science, and already federal agencies are wondering what level of authority they have in interpreting and enforcing regulations.

For example, a federal judge in Mississippi has already ruled that the U.S. Department of Health and Human Services can’t enforce a rule that would ban discriminating against patients on gender identity and sexual orientation. The Guardian recently reported that the Air Force is refusing to clean up water it polluted, “claiming federal regulators lack authority.”

The 6-3 decision by the Supreme Court could certainly affect the environment and public lands, but first, it’s important to understand exactly what the Chevron deference is all about.

What is the Chevron deference?

In 1984, the United States Supreme Court ruled that courts should defer to a regulatory agency’s reasonable interpretation of an ambiguous statute. If the law is unclear on water, for example, courts would defer to the Environmental Protection Agency’s (EPA) interpretation. In essence, it allowed judges to consider the expertise of the experts when ruling on a given case.

The case, Chevron U.S.A. Inc. v. Natural Resources Defense Council, Inc., defined the division of authority between courts and agencies, in this case, the EPA. The ruling raised the point that even though judges make the final rulings, they often need the expertise or specialized knowledge to make the decision accurately.

The opinion marked “a significant shift in the justification for giving deference to agency interpretations of the law,” wrote Columbia Law School professor Thomas W. Merrill in an article  about how this seemingly minute court case became what he terms an accidental landmark.

Merrill said this decision established a two-step framework for reviewing agency interpretations. First, the agency must explain how the regulation is ambiguous. “If the intent of Congress is clear, that is the end of the matter; for the court, as well as the agency, must give effect to the unambiguously expressed intent of Congress.”

The second step lays a path forward for the courts if there is no clear congressional intent or if the case involves industry-specific knowledge and specialized language and processes. According to Merrill, “the two-step formula also implied that deference to the agency interpretation was all-or-nothing.”

This minor detail shows how this ruling became a landmark case and one used to bolster the effectiveness and authority of the EPA and other federal agencies.

The Chevron deference was a bedrock doctrine that underlined challenges or defenses of federal land management and environmental rules. It was not pro- or anti-environment. Instead, it infused land management agencies with the ability to adapt law and policy to specific on-the-ground circumstances, which are rapidly evolving due to climate change.

“Federal land management agencies rely on [the Chevron deference] because it gave them latitude to interpret laws and craft regulations based on their expertise,” wrote Jonathan Thompson, a writer covering land issues for nearly two decades. His latest project, The Land Desk, is a newsletter focused squarely on the Western landscape.

Thompson wrote that this ruling provided agencies the confidence that regulations would stand up to legal challenges. The ruling “has probably influenced land regulations subtly but significantly — and probably in ways that we don’t even know about.”

Already, the lack of the Chevron deference is raising alarms. This ruling had become essential in managing Western lands due to the complexities and evolving science that govern the landscape, which is further complicated under climate change.

“It [was] an imperfect doctrine, but one that infuses the folks doing the hard work of managing the Western U.S.’s public lands, waters, and wildlife with a measure of needed ability to adapt law and policy to specific on-the-ground circumstances,” said Erik Schlenker-Goodrich, executive director of the Western Environmental Law Center, a nonprofit public interest environmental law center. He has also been an attorney working on federal ecological litigation, policy, planning, and decision-making in the western U.S. for over two decades.

Without the deference in place, Schlenker-Goodrich said private interests can “achieve, through litigation, what they have been unable to achieve through the political system.”

Without the deference

Special interests can now be more emboldened to bring cases to the high courts challenging agencies’ science- and fact-based decisions. With the Chevron deference effectively kicked to the curb, the knowledge-backed authority of agencies on land management now holds far less authority in the courts.

The Bureau of Land Management (BLM) manages most of the public land in Nevada, but at the time of this writing, the agency did not comment on the ruling.

“The Supreme Court’s decision is actively being weaponized by interests hostile to climate and conservation action to undercut the federal government’s ability to properly apply science and facts to the law in an adaptive fashion to respond to intensifying risks of aridification, catastrophic wildfire, and watershed degradation,” said Schlenker-Goodrich.

“My expectation is that the Supreme Court’s ill-advised decision to overturn the Chevron doctrine will sow chaos and litigation for years to come,” he said.

Consider this hypothetical scenario: A group takes a case about federal agencies rounding up wild horses to a high court, perhaps eventually to the U.S. Supreme Court. A biologist with the BLM is a witness for the agency due to their extensive knowledge of feral horses’ impact on desert riparian zones. This scientist testifies (using their first-hand experience) that wild, feral horses aggregate in numbers around springs and trample vegetation. The biologist explains that if nothing is done to mitigate impacts from wild horses, springs could be destroyed and water access for native wildlife could be eliminated. With the deference no longer in use, judges can dismiss the research and experiences when ruling on the case.

Editor’s note: The Sierra Nevada Ally does not take a stance on how federal agencies manage wild horse populations. The above example is purely illustrative.

“The risks to the health and integrity of Western U.S. ecosystems are very much at stake,” said Schlenker-Goodrich.

Land managers’ ability to manage public lands and protect intact landscapes and ecosystems the way they see fit is now in danger. These agencies still have the power to make regulations, but those rules may not be as resilient to future legal challenges. How the agencies draft rules and regulations may begin to change and have built-in protections. Without the Chevron deference, interest groups and corporations are now more spirited to challenge rules and federal agencies in court.

Without this scientific expertise informing the courts, a very different picture of public lands and the environment could be painted moving forward. Though no one can predict the potential impact, environmental restoration efforts have already been side-stepped through this legal shift.

However, there is a possibility that advocacy groups also have more power to challenge bad rules and regulations. “But now it all depends on the courts,” explained Thompson.

“If you’ve got bad judges, it’s not going to help.”