In its most important environmental ruling of recent decades, the Supreme Court decided in 2007 that the greenhouse gases blamed for warming the planet can be regulated as air pollutants under the Clean Air Act of 1990.

It was a pivotal opinion that opened the door for the Environmental Protection Agency to impose new regulations on autos, power plants, manufacturers and others, to address climate change as well as the dirty air targeted by the original law.

But it came on a 5-4 vote, with Justice Anthony M. Kennedy joining the four liberals and over a fierce dissent by Chief Justice John G. Roberts Jr.

Now as federal appellate Judge Brett M. Kavanaugh seeks to replace the retiring Kennedy on the Supreme Court, Kavanaugh’s 12-year record of skepticism toward such agency actions puts the landmark decision and other environmental protections at risk. Environmentalists fear that if Kavanaugh joins the court, he would vote to block anti-pollution regulations for decades, long after President Trump has departed.