The U.S. Supreme Court will hear arguments Wednesday in an important environmental case that centers on the obligation to be a "good neighbor."

Lawyers representing three states, companies and industry groups will ask the justices to block a federal rule that's intended to limit ozone air pollution. Experts said it's only the third time in more than 50 years that the court has scheduled arguments on an emergency application like this one.

At the heart of the dispute is the part of the Clean Air Act known as the "good neighbor" provision. It's designed to help protect people from severe health problems they face because of pollution that floats downwind from neighboring states.

"Air pollution doesn't respect state borders," said Harvard Law School professor Richard Lazarus.

The facts of the case

States like Wisconsin, New York and Connecticut can struggle to meet federal standards and reduce harmful levels of ozone because of emissions from coal plant smokestacks, cement kilns and natural gas pipelines that drift across their borders.

"One of the primary reasons that Congress passed this law in 1970 was the one place you could not trust the states to do it on their own was when there was interstate air pollution," Lazarus said.

Vickie Patton, general counsel at the Environmental Defense Fund, said these bedrock protections can save lives.

"There are children, there are older adults, people who work outside in the summer and people who are afflicted by asthma who are at very, very serious risk, and this case is just about asking those upwind polluters to do their fair share," Patton said.

Three of those upwind states — Ohio, Indiana and West Virginia — alongside companies including Kinder Morgan Inc. and U.S. Steel Corp. want the Supreme Court to freeze the good neighbor rule while they pursue an appeal with a lower court in the D.C. Circuit.

The Supreme Court steps in early

Stephen Vladeck, a law professor at the University of Texas and author of a book putting these kinds of emergency actions by the Supreme Court into context, said the other two cases where the justices entertained arguments at this stage involved vaccine mandates during the coronavirus pandemic.

The good neighbor case, on the other hand, doesn't present those same kinds of issues, he said.

"If this is an emergency, what isn't?" Vladeck asked. "There are lots of federal polices that are going to have massive stakes and they're going to have massive stakeholders on both sides. It's not at all obvious why this case merits this kind of special treatment."

Traditionally, the Supreme Court goes last — after a case has made its way through the lower courts and a variety of facts and arguments have been aired.

"This case hasn't really gone very far at all," Vladeck said. "I mean, the only thing that's happened in the entire litigation to date is that the D.C. Circuit, the federal appeals court, refused to give the same thing that they're now asking the Supreme Court for, refused to basically pause the rule at the beginning of the litigation."

The rule in question

Lawyers for the states and companies challenging the good neighbor rule declined to talk before the arguments. In court papers, they call the EPA rule a "disaster" and "a shell of itself."

That's because the plan originally applied to 23 states. But lower courts have hit pause in about half of them for a bunch of different reasons, in separate litigation.

These lawyers said states shouldn't have to shoulder the costs for what they say is an unlawful federal mandate, criticizing the EPA for taking a "top-down" approach to the rule.

But environmental advocates say many of the obligations in the new rule won't kick in until 2026, giving big polluters a couple of years to prepare. The rule is already in force and protecting people in a number of states, they add.

Lazarus, at Harvard Law School, said to win a pause at the Supreme Court, the states challenging the rule will have to meet what's typically a high bar by showing they're likely to win on the merits and they're suffering irreparable harm.

A skeptical Supreme Court

Even so, Lazarus said, regulators and environmental advocacy groups have had a hard time at the Supreme Court over the past few years. First, the justices struck down the Clean Power Plan. Then, they slashed the EPA's jurisdiction over the Clean Water Act. And just last month, they seemed skeptical about another case involving regulations for the fishing industry.

"It certainly seems like a court is sort of on a juggernaut to cut back in an aggressive way on sort of federal environmental law," he added.

Patton, whose environmental group submitted a friend of the court brief in the case, said she'll be watching closely.

"Industry has a responsibility to be a good neighbor under our nation's clean air laws, and I hope the Supreme Court does not upend those protections," Patton said.

There's no clear timetable for a decision from the justices.