The U.S. Supreme Court in a major environmental decision on Thursday overturned the Environmental Protection Agency’s definition of wetlands that fall under the agency’s jurisdiction, siding with an Idaho couple who’d said they should not be required to obtain federal permits to build on their property that lacked any navigable water.

All nine justices agreed to overturn the 9th Circuit Court of Appeals’ ruling that endorsed the Biden administration’s broad definition of waters of the United States, or WOTUS, the term for what falls under federal enforcement of the Clean Water Act.

But they published four separate opinions that showed a 5-4 split in how far they would allow federal jurisdiction to extend, with the conservative majority ruling to significantly narrow federal agency power.

“It is a substantial change to the way wetlands have been regulated under the Clean Water Act” since the law’s 1972 enactment, said Ashley Peck, an environmental litigator and water quality adviser at Holland and Hart LLP. “It looks like it will eliminate jurisdiction for a huge amount of wetlands, particularly in the arid West.”

Conservative Justice Brett M. Kavanaugh and the court’s three liberals concurred with the ruling in favor of Idaho landowners Michael and Chantell Sackett, but objected to the majority’s narrow new standard, which they said introduced more uncertainty and would hurt water quality.

The Sacketts had sought to build on a piece of their property separated by a 30-foot road from a tributary to Priest Lake in the Idaho panhandle. Lower courts held they needed federal environmental approvals because of their land’s connection to Priest Lake.

The Supreme Court heard oral arguments in their appeal in October.

‘Continuous surface connection’ test

Writing for the court’s majority, Justice Samuel Alito said the Clean Water Act applies only to wetlands with a “continuous surface connection” to the navigable waters like streams, lakes, oceans and rivers that are indisputably covered by the law.

The Biden administration’s definition — that said an area with an ecologically “significant nexus” to a navigable waterway was subject to Clean Water Act enforcement — would put nearly all waters and wetlands in the country under federal jurisdiction, with little room for state enforcement, Alito wrote.

Wetlands must be virtually indistinguishable from the navigable waters for federal jurisdiction to apply, he wrote.

That standard would limit the EPA and Army Corps of Engineers’ authority to regulate wetlands, even in areas where no one had disputed federal power.

Alito, who was appointed to the court by President George W. Bush, praised the Clean Water Act for effectively curtailing water pollution. But he said the law “is a potent weapon” with severe penalties, and its power should be checked.

The text of the law uses both the terms “navigable waters,” which has a well-known definition, and “waters of the United States,” which does not, Alito wrote.

The EPA, Army Corps of Engineers and various courts have held that waters of the United States can include tributaries to navigable waters and even dry land with an ecological connection to those tributaries.

The inclusion in the statute of “navigable waters” means Congress was focused on the permanent lakes, rivers, streams and oceans that are generally included in that definition, even if some wetlands can also be regulated under the law, Alito wrote.

“Although we have acknowledged that the CWA extends to more than traditional navigable waters, we have refused to read ‘navigable’ out of the statute,” Alito said.

Some adjacent wetlands can still be considered waters of the United States, Alito said. But for the federal law to apply to a wetland, it “must be indistinguishably part of a” covered water, he wrote.

The ruling represents a sweeping shift in wetlands regulation, even for a conservative court with a recent history of restricting federal regulations.

“This was a broader brush than I expected,” Peck said. “This is always a possibility with this court, for certain, but I wasn’t necessarily expecting to have the whole regulatory regime upended.”

Kavanaugh and liberals band together

Kavanaugh, with the court’s three liberals joining, wrote that a continuous surface connection to navigable waters was not strictly necessary for wetlands to fall under federal jurisdiction. Waters can be adjacent without that connection, they said.

Kavanaugh, in a notable departure from the usual alliance on the court, said the majority rewrote the law and introduced new questions about wetlands that have long been subject to federal jurisdiction.

“The Court’s new and overly narrow test may leave long-regulated and long-accepted-to-be-regulable wetlands suddenly beyond the scope of the agencies’ regulatory authority, with negative consequences for waters of the United States,” he wrote.

Kagan blasts judicial policymaking

Justice Elena Kagan wrote a separate concurring opinion with fellow liberal Justices Sonia Sotomayor and Ketanji Brown Jackson that criticized the court for policymaking.

Drawing parallels with her dissent in a decision last year that restricted the EPA’s power to regulate carbon emissions at existing power plants, Kagan wrote that the court’s conservatives simply substituted their policy preferences for what Congress actually enacted.

The majority in this case invented a standard that laws that impact private property must have “exceedingly clear language,” Kagan wrote, putting “a thumb on the scale for property owners,” and disregarding the public interest in clean water.

“A court may not rewrite Congress’s plain instructions because they go further than preferred,” she said. “That is what the majority does today in finding that the Clean Water Act excludes many wetlands (clearly) ‘adjacent’ to covered waters.”

Lengthy legal fight

The case is part of a decades-long legal conflict to define the reach of the Clean Water Act.

Alito’s majority opinion referenced the years of shifting definitions and the uncertainty provided in various court cases and agency regulations, calling it “the persistent problem that we must address.”

In general, agricultural interests, home builders and Republican officials have argued that the federal regulations impose an undue burden and should be applied narrowly.

“The Supreme Court just ruled that Biden’s overreaching WOTUS interpretation is unconstitutional,” Missouri Attorney General Andrew Bailey, a Republican, said on Twitter. “This is a huge win for farmers across America.”

Environmental groups and Democrats have argued for a broader definition that they say allows the federal government to offer important protections.

“Federal protections that don’t depend on local politics or regional polluter influence are essential to vulnerable and disadvantaged communities nationwide,” Jim Murphy, the director of legal advocacy for the National Wildlife Federation, said in a statement “The court’s ruling removes these vital protections from important streams and wetlands in every state.”

Murphy called on Congress and state governments to adopt stronger standards.

The ruling doesn’t necessarily limit the issue’s long-running uncertainty, Peck said. While it settles federal jurisdiction for now, states, especially in the West, may decide to strengthen their own clean water laws and regulations, she said.

Reaction from Congress

Several Republicans in Congress responded to the ruling with enthusiasm.

“The Supreme Court’s decision is clearly a decisive win for America’s farmers, small businesses, property owners, and those who help build our infrastructure,” U.S. House Transportation and Infrastructure Chairman Sam Graves of Missouri and Water Resources and Environment Subcommittee Chairman David Rouzer of North Carolina said in a joint statement.

“This is great news for rural America!” Minnesota Republican Pete Stauber, the chairman of the U.S. House Natural Resources Subcommittee on Energy and Mineral Resources, tweeted.

“I’m glad to see the Supreme Court rightfully and unanimously blocked Biden’s ill-conceived #WOTUS rule,” U.S. Sen. Joni Ernst of Iowa wrote on Twitter. “This is a big WIN for Iowa, where nearly every industry is impacted.”

“Kansans are best positioned to conserve our land and natural resources,” Kansas Republican U.S. Rep. Ron Estes said. “And they don’t need Biden’s bureaucrats 1000 miles away to regulate the rainwater that accumulates in ditches in rural parts of our state.”

Fewer Democrats publicly commented on the ruling, but Senate Environment and Public Works Chairman Tom Carper of Delaware said the decision undermines the EPA’s ability to effectively regulate water pollution and puts “America’s remaining wetlands in jeopardy.”

“I strongly disagree with the Court’s decision, and I am deeply concerned about the future impacts of this case on clean drinking water, coastal and flood-prone communities, and wildlife across our nation,” Carper said.

This story has been updated.