Alito's recusal leaves Exxon and Suncor needing five of eight justices to stop Boulder's climate suit

Boulder filed its lawsuit against Exxon and Suncor in 2018, raising claims under state law that the companies' production and allegedly deceptive marketing of fossil fuels contributed to climate change.

The case has not yet gone to trial in Colorado.

Exxon and Suncor unsuccessfully tried to move the case to federal court, were denied dismissal by the Boulder County District Court, and lost at the Colorado Supreme Court before appealing to the U.S. Supreme Court.

Justice Ketanji Brown Jackson said review was "premature," telling Harris: "It feels like we don't really know enough to be confident that the theories that you are proposing are actually applicable here."

The Trump administration is backing Exxon and Suncor; principal deputy solicitor general Sarah Harris said Boulder's lawsuit "egregiously exceeds" constitutional limits of state authority.

Justice Brett Kavanaugh repeatedly said that four Supreme Court decisions dating back to 1972 make clear that interstate air and water pollution are matters of federal law.

"We don't have to reinvent the wheel, because we've said this multiple times," Kavanaugh said.

The decision could have broad ramifications for more than two dozen similar lawsuits brought by cities and counties around the country.

Boulder's lawsuit is one of dozens filed by states and local governments against energy companies in state courts seeking money damages for climate-related harms.

Chief Justice John Roberts said: "Presumably, if you prevail, just the next day, a municipality in every single state will file a lawsuit, they'll probably copy your pleadings, and then there will be at least 50, you know, different cities ... causes of action filed."

Roberts asked Shanmugam whether he would concede that in some situations an individual whose conduct in State B causes harm in State A can be sued under the law of State A; Shanmugam replied, "We would concede that."

Shanmugam said: "If Boulder's claims are allowed to go forward, some 90,000 municipalities across the country will have the ability to make national and international energy policy by asking juries to impose catastrophic damages on selected fossil-fuel producers."

The companies deny the allegations and warn that if the Boulder lawsuit and others like it move forward to trial, energy companies could face crippling damages in the billions of dollars.

One possibility is that the court simply dismisses the case, which would allow litigation to continue.

Justice Elena Kagan likened the suit to tobacco and opioid litigation: "I'm waiting to see the distinction," said Kagan.

Kagan said a ruling that state lawsuits are pre-empted by the Clean Air Act could be "the more natural and simpler route" if the court sides with the companies; that would be the narrower of two paths, with Shanmugam pushing for a broader ruling that state lawsuits are prohibited under the Constitution.

Roberts seemed skeptical that the lawsuit was anything other than what he called "an effort to reduce emissions."

Roberts' estimate of at least 50 suits is roughly double the more than two dozen similar local-government suits NBC counts.

With eight justices sitting and a 4-4 tie leaving the Colorado ruling in place, Exxon and Suncor need a five-vote majority to end the case.

Of the four outcomes described (Boulder win, 4-4 tie, dismissal, company majority), three leave the case proceeding in state court.

Justice Sonia Sotomayor said: "The Clean Air Act does not regulate marketing or advertising of fuel, correct?"

Boulder Mayor Aaron Brockett said: "It's taken a long time to get to this point, but it feels very positive that that effort that we started in this exact location eight years ago has gotten to the stage of going to the Supreme Court, and then hopefully the next step of having a full hearing in court."

The Trump administration's EPA has made recent efforts to eliminate greenhouse gas regulations under the Clean Air Act, an issue being litigated.