His reasoning ultimately persuaded the Supreme Court’s conservative justices, who later overruled the lower court and voted 5-4 to strike down parts of the E.P.A.’s permitting program that Judge Kavanaugh found troubling.

“I do believe the Supreme Court paid attention to Kavanaugh’s opinions on administrative law,” said Jonathan H. Adler, a law professor at Case Western Reserve University. “He lives and breathes this stuff, he’s been doing it for a long time, and that sort of experience matters when you’re dealing with complex regulatory issues.”

In other cases, however, Judge Kavanaugh went even further than the Supreme Court’s conservative wing was willing to go. In E.M.E. Homer City Generation v. Environmental Protection Agency, he wrote a majority opinion for the D.C. Circuit Court striking down a federal program to regulate air pollution that crossed state boundaries. The Supreme Court later took up the case and overruled him 6-2, with Justice Kennedy and Chief Justice John G. Roberts Jr. voting to uphold the pollution rule.

That case, along with several others, have led some legal experts to conclude that Judge Kavanaugh would, if confirmed, push the Supreme Court to be far more hostile to federal regulations. Such a shift could clear the way for the Trump administration to roll back Obama-era environmental policies in the coming years.

“It’ll be a very different court in the future,” said Robert Percival, a professor of environmental law at the University of Maryland. “Kennedy at least had an open mind on this issue, but if he’s replaced by Kavanaugh, it will really be hard times for environmental law for the rest of my lifetime.”

Other experts point out, however, that Judge Kavanaugh has not always reflexively voted against environmental regulations. In 2013, for instance, he voted to uphold a contentious E.P.A. decision to retroactively veto a West Virginia mining project. And in a 2014 opinion, Judge Kavanaugh ruled in favor of the Natural Resources Defense Council, an environmental group that had criticized an industry-friendly provision in a federal rule involving emissions from cement kilns.

“I can’t say environmental groups should be celebrating,” Mr. Lazarus said. But, he added, “I don’t think you can look at all these cases and say this is someone who is single-mindedly hostile toward environmental lawmaking.”

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