The Supreme Court hears argument today in EPA v. EME Homer City Generation — a challenge to the Environmental Protection Agency’s Cross-State Air Pollution Rule. Simply put, pollution generated by factories in upwind states inevitably drifts downwind into states like Rhode Island, putting the health of millions of citizens in those states at risk. With the Clean Air Act, Congress gave the EPA authority to address this problem — authority that the EPA used to design the new rule at issue in EME Homer. However, the D.C. Circuit Court struck it down last year in a 2-1 decision.

Rhode Islanders have particular cause to pay close attention to EME Homer. According to the EPA, the regulation would save the state between $260 million and $650 million in health costs annually — to say nothing of the lives it will save. Sen. Sheldon Whitehouse (D-R.I.), who fought cross-state pollution as Rhode Island’s attorney general a decade ago, has correctly said that the costs of pollution are “paid in lives and reduced quality of life.”

These costs ought to make EME Homer a case worth watching, but here are five more reasons to keep an eye on it:

•  This Supreme Court term is shaping up to be the biggest one for the environment since the Roberts court decided Massachusetts v. EPA in 2007. The court is slated to decide not just EME Homer this term, but also a challenge to the EPA’s recent efforts to regulate greenhouse-gas emissions. With the Obama administration pressing ahead with new regulations, this term may offer important clues as to where the Roberts court — and especially Justice Anthony Kennedy — will stand in key environmental cases moving forward.

•  EME Homer is the first big case of the term for the U.S. Chamber of Commerce, which weighed in with an amicus brief in support of those challenging the EPA’s new rule. The Chamber has won the vast majority of its cases before the Roberts court overall — and a staggering 88 percent of them since October 2011. Moreover, the Chamber has gone 8 and 2 in its environmental cases since Chief Justice John Roberts and Justice Samuel Alito joined the court. Since its defeat in Mass. v. EPA, the Chamber is on a seven-case winning streak in environmental cases overall. Will this winning streak continue in EME Homer?

•  When they drafted and ratified the U.S. Constitution, the Founders envisioned a national government with the power to address genuinely national problems, including problems that spilled across state lines and threatened interstate comity. Cross-state air pollution is just this sort of problem. When Congress and the executive branch are acting to address it, their efforts are entitled to great deference from the judiciary.

•  EME Homer presents an intriguing legal dilemma for members of the Roberts court’s conservative wing. Usually, when a lower-court judge loosens procedural rules to let parties raise new arguments that should have been raised in earlier proceedings and then goes on to read certain policies into, at best, an ambiguous statute (and over and above a contrary interpretation by a government agency), he can expect a rough welcome from the court’s conservatives.

Will conservative favorite Brett Kavanaugh — called out for both of these judicial crimes by Judge Judith Rogers in her EME Homer dissent — receive similar treatment? And how will Justices Antonin Scalia and Clarence Thomas respond, given that they both reaffirmed their commitment to deferring to government agencies just last term in City of Arlington v. FCC?

•  Judge Kavanaugh plays a leading role in both of the big environmental cases before the court this term, having written the majority opinion in EME Homer and an important dissent in the greenhouse-gas cases. More important, he’s a rising star in the conservative legal firmament — a former clerk to Justice Kennedy who went on to work on the Starr Report and then as an aide to President George W. Bush.

Given his impressive credentials, Judge Kavanaugh would probably be on any Republican president’s Supreme Court short list. And his current position on the D.C. Circuit makes this all the more likely. Just ask Chief Justice Roberts, as well as Justices Ruth Bader Ginsburg, Scalia, and Thomas — all of whom served on the D.C. Circuit before joining the Supreme Court.

Not only does EME Homer offer a slew of important legal angles, but, according to the EPA, thousands of lives hang in the balance. Whether you’re a legal junkie who lives and breathes Supreme Court cases, or a concerned Rhode Islander who breathes air, you have a reason to watch this case closely.

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A version of this piece also appeared in the online journal grist.