A sharply divided Supreme Court on Thursday significantly rolled back federal safeguards for wetlands under the Clean Water Act, siding with Idaho property owners in a decision that curbs Environmental Protection Agency power.
The case, Sackett v. EPA, pitted Michael and Chantell Sackett against EPA regulators over a bid to build a family home adjacent to Priest Lake in northern Idaho.
The government said their land qualifies as a protected wetland, requiring an expensive permit for construction, while the family argued that its property is not directly connected to the lake and that the broad EPA regulations are an overreach.
The Clean Water Act of 1972 allows the government to set rules for pollution in "waters of the United States," but for years, the extent to which adjacent wetlands are covered by the law has been hotly debated and unclear.
In 2017, a fractured Supreme Court said that the EPA can regulate any wetlands with a "significant nexus" to navigable waters, like rivers, lakes and oceans.
But Thursday, Justice Samuel Alito, writing for a five-justice majority in the Sackett case, said the existing standard is too broad, too difficult to enforce and too "precarious" for property owners.
"We hold that the [Clean Water Act] extends to only those wetlands that are as a practical matter indistinguishable from waters of the United States," Alito wrote.
He said the EPA could only regulate wetlands adjacent to a "relatively permanent body of water connected to traditional interstate navigable waters" and having a "continuous surface connection with that water, making it difficult to determine where the 'water' ends and the 'wetland' begins."
"Wetlands that are separate from traditional navigable waters cannot be considered part of those waters, even if they are located nearby," Alito wrote.
MORE: Chief Justice John Roberts defends Supreme Court's 'highest standards of conduct,' offers no new rulesThe decision will in effect significantly reduce the number of wetlands protected by the Clean Water Act. It will also provide property owners with greater clarity and flexibility in utilizing their land free from government regulation.
"The Court's ruling returns the scope of the Clean Water Act to its original and proper limits," said Damien Schiff, a senior attorney at Pacific Legal Foundation 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."
Alito was joined by Chief Justice John Roberts and Justices Clarence Thomas, Neil Gorsuch and Amy Coney Barrett in adopting the new, more stringent "continuous surface connection" standard for which wetlands are protected.
All of the justices agreed that the Sacketts' property, specifically, should not have been regulated as a wetland under the Clean Water Act, but Trump-appointed Justice Brett Kavanaugh joined liberal Justices Elena Kagan, Sonia Sotomayor and Ketanji Brown Jackson in strongly arguing that the majority had gone too far with its reasoning.
"By narrowing the Act's coverage of wetlands to only adjoining wetlands, the Court's new test will leave some long-regulated adjacent wetlands no longer covered by the Clean Water Act, with significant repercussions for water quality and flood control throughout the United States," Kavanaugh wrote for the minority.
EPA administrator Michael Regan said the agency was disappointed by the high court's decision and that it "erodes longstanding clean water protections."
"The Biden-Harris Administration has worked to establish a durable definition of 'waters of the United States' that safeguards our nation's waters, strengthens economic opportunity, and protects people's health while providing the clarity and certainty that farmers, ranchers, and landowners deserve," Regan said in a statement. "These goals will continue to guide the agency forward as we carefully review the Supreme Court decision and consider next steps."
The White House said the decision "aims to take our country backwards."
"It will jeopardize the sources of clean drinking water for farmers, businesses and millions of Americans," press secretary Karine Jean-Pierre said at her on-cam briefing Thursday afternoon.
Environmental groups said the decision is a huge setback.
"The Sackett decision undoes a half-century of progress generated by the Clean Water Act. Almost 90 million acres of formerly protected wetlands now face an existential threat from polluters and developers," said Sam Sankar, vice president of Programs at Earthjustice, an advocacy group that had weighed in on the case.
Sierra Club Executive Director Ben Jealous said the weakened rules would have a direct impact.
"Millions of Americans will have less safe drinking water than the generation before them," Jealous said in a statement. "This fight is far from over."
Biden administration lawyers are "carefully reviewing the decision," per Jean-Pierre.
ABC News' Benjamin Gittleson contributed to this report.