The Supreme Court narrowed the protections of the Clean Water Act in an opinion Thursday, finding the law only covered wetlands and other bodies of water that directly connect to federal waters like rivers and lakes.

The opinion issued in Sackett v. Environmental Protection Agency reversed a Ninth Circuit ruling that a pair of Idaho landowners’ property was subject to regulation under the CWA. Justice Samuel A. Alito Jr., wrote for five conservative justices that the law’s protections for “Waters of the United States” only extended to wetlands with a direct surface connection to them, which did not include the Sacketts’ property.

“In sum, we hold that the CWA extends to only those ‘wetlands with a continuous surface connection to bodies that are ‘waters of the United States’ in their own right,’ so that they are ‘indistinguishable’ from those waters,” the opinion said.

Thursday’s opinion replaced the court’s 2006 splintered decision that provided two different tests for determining whether waters were regulated. The 1972 law has been subject to litigation for much of its existence as property owners and the federal government wrestled with how far to extend its protections against polluting the navigable waters of the country.

The Biden administration had argued language in the law should include wetlands and other bodies of water that didn’t have a direct surface connection but could allow pollutants into rivers and lakes.

However the majority of the Supreme Court disagreed, finding that interpretation of the law was too vague especially considering the criminal penalties attached to violations.

“This freewheeling inquiry provides little notice to landowners of their obligations under the CWA,” the opinion said.

Justice Clarence Thomas and Neil M. Gorsuch filed another concurring opinion that agreed with the judgment and would have gone farther. Thomas wrote that the law should only cover those waters directly used for interstate commerce.

Justices Brett M. Kavanaugh, Elena Kagan, Sonia Sotomayor and Ketanji Brown Jackson filed a concurring opinion that criticized how far the majority restricted the CWA. Kavanaugh and the others would have reversed the Ninth Circuit ruling but criticized the new test Alito and the majority adopted.

“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.

Kagan, Sotomayor and Jackson went further in another concurring opinion they filed. The trio said the majority put its finger on the scale for property owners fighting pollution laws by inventing a new rule where Congress had to make a “clear statement” of the federal government’s power over private property use.

That is allowable when Congress passed an ambiguous law, “But a court may not rewrite Congress’ plain instructions because they go further than preferred,” Kagan’s opinion said.

“That is what the majority does today in finding that the Clean Water Act excludes many wetlands (clearly) ‘adjacent’ to covered waters,” the concurrence said.

President Joe Biden, in a statement, said that his team will work with the Justice Department and relevant agencies to review the decision “and use every legal authority we have to protect our Nation’s waters for the people and communities that depend on them.”

“Since the Clean Water Act was passed by an overwhelming bipartisan majority in Congress in 1972, it has been used by Republican and Democratic administrations alike to help ensure Americans in every state have clean water,” Biden said. “It is the reason why today America’s lakes are swimmable, why we can fish in our streams and rivers, and why clean water comes out of our taps.”

The justices heard the case before the Biden administration finalized a new rule for the waters of the United States, which became an issue during oral arguments.

The administration adopted its new three-factor test earlier this year and it went into effect in March. The rule, which been subject to extensive litigation and is enjoined from being enforced in more than two dozen states, reflected the administration’s position in the case by placing under the law wetlands with a “significant nexus” to regulated waters. 

It was not immediately clear Thursday what effect the opinion may have on the ongoing litigation over the Biden administration rule.