Brett Kavanaugh broke from his fellow conservative Supreme Court justices and warned their ruling on the EPA could jeopardize water quality and flood control

• A Supreme Court ruling issued Thursday undercuts the EPA’s authority to regulate under the Clean Water Act.
• Every conservative justice besides Brett Kavanaugh signed onto the majority opinion.
• Kavanaugh said the majority was ignoring precedent and jeopardizing water quality in the US.

The Supreme Court issued a ruling Thursday that will limit the Environmental Protection Agency’s ability to protect wetlands and address water pollution, with all but one conservative justice, Brett Kavanaugh, signing off on it.

The case concerned a couple in Idaho who wanted to build a home on their property, but the EPA determined the land included wetlands that were protected under the Clean Water Act, subjecting it to the agency’s oversight.

All nine justices agreed that the couple’s land should not have been subject to regulation, but four justices — the liberal wing and Kavanaugh — sharply disagreed with part of the majority ruling, written by Alito, that could impact what exactly counts as protected “waters of the United States.”

The majority ruling determined that the Clean Water Act does not have the authority to regulate wetlands unless they have a “a continuous surface connection” to larger bodies of water. That could exclude wetlands, bogs, and marshes that are adjacent to a body of water if not exactly connected on the surface, and that have been previously considered protected.

Some environmental groups and experts have estimated that the decision could remove protections for nearly half of all wetlands in the US.

Kavanaugh’s concurring opinion, signed on by the liberal justices, said that the majority’s “new test for assessing when wetlands are covered by the Clean Water Act” runs counter to the law, departs from decades of agency practice, and contradicts precedent set by the Supreme Court itself.

“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.

In addition to joining Kavanaugh, the liberal justices also signed a concurring opinion written by Justice Elena Kagan raising concerns that the Supreme Court is overriding Congress’s authority when it comes to environmental policy. She cited a ruling last year that limited the EPA’s ability to regulate greenhouse gases and address climate change.

In another concurring opinion, Justice Clarence Thomas suggested he’d be interested in curbing the EPA’s authority even further, writing “wetlands are just the beginning of the problems raised by the agencies’ assertion of jurisdiction in this case.”