The air you breathe is about to get a little cleaner. And for that you can thank Justice Ruth Bader Ginsburg.

The U.S. Supreme Court on Tuesday issued a key decision, written by Ginsburg, upholding a regulation called the Cross-State Air Pollution Rule. The “good neighbor rule,” as it’s come to be known, seeks to address air pollution that travels hundreds of miles away from its original source—say, from Ohio to New England—by requiring about 1,000 aging coal plans in 28 states to cut the harmful pollutants that create soot and smog. The Environmental Protection Agency administers the regulation, using authority it has from the 1972 Clean Air Act.

The ruling was a rebuke to the fossil fuel industry, which has fought these regulations, and to a lower federal court, which in 2012 rejected them as unconstitutional. It did not appear to be a close call. Chief Justice John Roberts and Justice Anthony Kennedy joined the decision, giving it the imprimatur of a six-justice majority. Justices Antonin Scalia and Clarence Thomas dissented, suggesting the pollution control scheme verged on Marxism. (Justice Samuel Alito recused himself, presumably because of a conflict of interest.)

The decision didn’t get a ton of attention outside of environmental circles. But it’s a bona fide big deal. Here are four reasons why: