The US Supreme Court put new limits on the Clean Water Act, slashing the power of federal regulators to protect wetlands in a long-sought victory for a couple seeking to build a house near an Idaho lake.

Although the court was unanimous in backing landowners Chantell and Michael Sackett, the justices diverged sharply on their reasoning. Justice Brett Kavanaugh joined the court’s three liberals in saying the decision will undercut important environmental protections.

It’s the latest in a line of Supreme Court rulings that have restricted the authority of federal regulators. The decision comes less than a year after the court curbed the Environmental Protection Agency’s ability to address climate change.

The latest ruling could give companies a freer hand to discharge pollutants and could let developers construct more new houses without getting federal approval. It’s a victory for property-rights advocates and a defeat for environmentalists and the Biden administration.

The 1972 Clean Water Act gives the federal government control over “waters of the United States,” including rivers and lakes. Writing for five members of the court, Justice Samuel Alito said Thursday that wetlands are covered only if they have a continuous surface connection to one of those major waterways.

“We hold that the CWA extends to only those wetlands that are as a practical matter indistinguishable from waters of the United States,” Alito wrote. Chief Justice John Roberts and Justices Clarence Thomas, Neil Gorsuch and Amy Coney Barrett joined Alito’s opinion.

In a concurring opinion that read more like a dissent, Justice Elena Kagan said Alito’s test ignored the water law’s language and put “a thumb on the scale against the Clean Water Act’s protections.” She likened the ruling to the court’s climate change decision last June.

“The vice in both instances is the same: the court’s appointment of itself as the national decision-maker on environmental policy,” Kagan wrote in an opinion joined by Justices Sonia Sotomayor and Ketanji Brown Jackson.

Kavanaugh said he would have sided with the Sacketts on narrower grounds. Writing for himself and the three liberals, Kavanaugh said he read the law as covering wetlands that are separated from a major waterway only by a barrier like a dike or beach dune.

Kavanaugh said that distinction “will matter a great deal in the real world.” He said the court’s reasoning could endanger wetlands separated from the Mississippi River by its extensive levee system and allow the filling of important wetlands that protect the Chesapeake Bay.

Kavanaugh and Kagan both pointed to a 1977 provision that indicates the law covers “adjacent” wetlands.

Wetlands Value

Environmental groups said the ruling could strip tens of millions of acres of wetlands of federal protection.

“The Supreme Court ripped the heart out of the law we depend on to protect American waters and wetlands,” said Manish Bapna, president of the Natural Resources Defense Council. “This decision will cause incalculable harm. Communities across the country will pay the price.”

The decision “will increase flooding and lead to more pollution, jeopardizing the health of our communities, especially the health of communities of color and low-wealth communities who are disproportionately impacted by water pollution,” said Madeleine Foote, deputy legislative director with the League of Conservation Voters.

EPA Administrator Michael Regan said the ruling “erodes longstanding clean water protections.”

The Pacific Legal Foundation, a property-rights group that represents the Sacketts, hailed the decision.

“The court’s ruling returns the scope of the Clean Water Act to its original and proper limits,” said Damien Schiff, the PLF attorney who argued the case. “Courts now have a clear measuring stick for fairness and consistency by federal regulators. Today’s ruling is a profound win for property rights and the constitutional separation of powers.”

The court “sent a loud and clear warning shot to the Biden administration about its attempts to overregulate the lives of millions of Americans,” said Senator Shelley Moore Capito of West Virginia, the top Republican on the Senate Environment and Public Works Committee. “The court protected America’s farmers, ranchers, builders, and landowners from overreach under the Clean Water Act.”

Idaho Lake

The fight involves a 0.63-acre property near Priest Lake in northern Idaho. The property is about 300 feet (91 meters) from the lake and, on the other side, across a road from a tributary of a creek that feeds into the lake. The EPA says that the land is connected to the lake through a subsurface flow of water.

The Biden administration contended the tributary across the road brought the land within the scope of the Clean Water Act, particularly since the two properties were once part of the same wetlands complex. The administration said wetlands play a crucial role in protecting the integrity of nearby water bodies, even if they don’t have a surface connection.

The dispute began in 2007 when the EPA issued an administrative compliance order requiring the Sacketts to restore land they had already begun preparing for construction. The case has bounced up and down the court system since then, with the Supreme Court saying in 2015 the Sacketts could press a lawsuit.

A federal appeals court later said the Clean Water Act covered the property, prompting the Sacketts to turn again to the Supreme Court.

The Sacketts’ appeal asked the court to revisit a 2006 Clean Water Act case, Rapanos v. United States, which failed to produce a majority decision and left uncertainty about the governing standard. Four justices, led by Antonin Scalia, said the law covers wetlands only if they have a continuous surface connection to a major waterway.

A fifth, Justice Anthony Kennedy, created his own test, saying the Clean Water Act covers wetlands with a “significant nexus” to one of those larger bodies of water.

Alito on Thursday rejected the significant-nexus test, saying that “the boundary between a ‘significant’ and an insignificant nexus is far from clear.”

The case is Sackett v. Environmental Protection Agency, 21-454.

--With assistance from Emily Birnbaum and Jennifer A. Dlouhy.

(Adds in 12th paragraph that tens of millions of acres could be affected.)