The Supreme Court on Friday curtailed the power of federal agencies to regulate the environment, public health and other fundamental aspects of American life.

The 6-3 ruling, written by Chief Justice John G. Roberts Jr., could make it easier for courts to block regulations aimed at addressing air pollution, combating climate change and protecting endangered species, lawyers say.

Here’s what to know about the ruling and its potential impact on environmental protections in the United States:

The pair of cases — Loper Bright Enterprises v. Raimondo and Relentless, Inc. v. Department of Commerce —challenged a federal rule that requires the herring industry to cover the costs of observers on fishing boats.

In the decision released Friday, the Supreme Court struck down the rule, issued by the National Marine Fisheries Service, finding it to be overly burdensome. Lower courts had previously upheld the rule, finding it to be a reasonable interpretation of federal law.

The decision effectively overturns a long-standing precedent known as the Chevron doctrine.

The doctrine says that courts should defer to an agency’s interpretation of a law, as long as that interpretation is reasonable. It was established by the Supreme Court’s landmark 1984 ruling in Chevron U.S.A. v. Natural Resources Defense Council.

The 1984 decision represented a victory for the Reagan administration and a loss for environmental groups, including the Natural Resources Defense Council. Under President Ronald Reagan (R), the Environmental Protection Agency had issued a rule that allowed manufacturing plants to install or modify one piece of equipment without obtaining a federal permit.

Environmental groups had challenged the rule, saying it violated the Clean Air Act and would cause more air pollution. But in the unanimous 6-0 decision, Justice John Paul Stevens wrote that the court should defer to the EPA’s reading of the Clean Air Act, and to other agencies’ interpretations of other statutes.

At the time, Chevron was not seen as a historic ruling. But it became a major precedent once it filtered through the lower courts, and it eventually gave future administrations more power to issue stronger environmental rules than those of the Reagan era.

A wide array of conservative advocacy groups have urged the court to overturn Chevron. But petrochemicals billionaire Charles Koch has played a particularly influential role.

Both cases were backed by conservative legal organizations — the Cause of Action Institute and New Civil Liberties Alliance — that have received millions of dollars from the Koch network, founded by Charles Koch and his late brother, David Koch. Charles Koch is the CEO of Koch Industries and a fierce critic of federal regulations.

Asked about this funding, Ryan Mulvey, counsel at the Cause of Action Institute, said the focus should be on the fishermen.

“Like any public interest law firm, Cause of Action Institute took this case to defend the rights of individuals who do not have the resources to challenge unconstitutional actions on their own,” Mulvey said in an emailed statement. “This case has always been about vindicating their interests.”

Ironically, many environmental groups supported retaining Chevron, even though the original 1984 decision handed them a defeat.

Two heavyweights in the environmental movement — the Environmental Defense Fund and the Natural Resources Defense Council — both submitted amicus briefs urging the justices not to overturn Chevron. Three other conservation groups — Conservation Law Foundation, Ocean Conservancy and Save the Sound — also filed a joint brief in defense of the doctrine.

Additional support for Chevron came from a wide range of other individuals and groups, including Democratic senators, the American Cancer Society and the Lawyers’ Committee for Civil Rights Under Law.

Probably.

That’s according to David Doniger, senior strategic director of the climate and clean energy program at the Natural Resources Defense Council, who argued the Chevron case. Doniger said the ruling released Friday could prevent agencies from using older environmental laws to tackle newer environmental problems — such as climate change — as they arise.

“The real goal of the interest groups on the right that are backing this litigation is to enfeeble the federal government’s ability to deal with the problems that the modern world throws at us,” Doniger said. “We could end up with a weaker federal government, and that would mean that interest groups would be freer to pollute without restraint.”

Still, President Biden’s signature climate law gave the EPA more authority to curb planet-warming emissions, Doniger said. For the first time, the climate law, known as the Inflation Reduction Act, defined greenhouse gases as air pollutants that the EPA can regulate under the Clean Air Act.

Probably.

In litigation over protections for vulnerable plants and animals, courts have often deferred to the U.S. Fish and Wildlife Service’s interpretation of the Endangered Species Act. That could change in response to Friday’s ruling, said Damien Schiff, a senior attorney at the Pacific Legal Foundation, a conservative public interest law firm that supported overturning Chevron.

“Chevron has been invoked to justify a very broad level of discretion for how endangered species are protected,” Schiff said.

Probably not.

The EPA assesses the health risks posed by specific chemicals by interpreting scientific studies, not by interpreting ambiguous statutes, said Madeleine Boyer, a principal at the firm Beveridge & Diamond who represents clients in the chemical industry.

Chevron “isn’t intended to address the deference that should be given to an agency’s interpretation of its own facts and science,” Boyer said.

There could be a spike in lawsuits over actions by federal agencies — not only environmental agencies such as the EPA, but also the Departments of Education, Labor and Health and Human Services. It could take years for this litigation to play out.

In the meantime, the ruling could prompt Republican lawmakers on Capitol Hill to intensify their oversight of the Biden administration’s environmental rules, staff for the House Republican Study Committee wrote in a memo released Monday.

“If Chevron is rolled back or overturned, this will be a landmark decision which could open the door to Congress … rolling back Biden’s woke and weaponized administrative agenda,’ the memo says.