Vermont Law School professor Patrick Parenteau has given lots of interviews since Wednesday, when Supreme Court Justice Anthony Kennedy announced his retirement. Most have focused on how Kennedy’s absence from the court will help Scott Pruitt, the head of the Environmental Protection Agency, in his quest to vigorously dismantle America’s environmental protection laws.

But Parenteau says his interviews thus far have lacked an important sentiment: “No one talks about how weird it is,” he said. “It,” here, is the fact that the head of the EPA is actually attacking rules to protect clean air and water. The American public may have gotten used to Pruitt’s agenda, he said, but “This still isn’t a normal thing.”

Normal or not, it’s happening. Right now, the Pruitt EPA’s attempts to undo regulations around clean air, water, and the environment face court challenges by environmental groups and attorneys general in Democratic states. Should those cases reach the Supreme Court (and many will), Kennedy’s retirement and replacement will have a huge effect on how they’re decided. “There’s no happier person in America right now than Scott Pruitt,” he said.

Kennedy’s departure represents the loss of the Supreme Court’s so-called “swing vote”—the justice who most often determined whether a law was upheld or struck down. “One can comfortably say that he was the single most influential justice for environmental law over the past 30 years,” Richard J. Lazarus, a Harvard law professor, told The New York Times. “Many of those cases were sharply divided, but the one constant was that Kennedy was in the majority in every single case but one.”

If Kennedy is replaced with a someone ideologically similar to the late Justice Antonin Scalia or Associate Justice Neil Gorsuch, there could be lasting consequences—particularly for drinking water and climate change. That’s because Kennedy’s swing vote paved the way for two major Obama-era regulations that Pruitt is now trying to weaken: The Clean Power Plan and the Waters of the United States rule.