The Question the Court Added

The first case of the Supreme Court’s new term was filed in Boulder County District Court in April 2018, and it has still not reached a trial. The city and county of Boulder sued ExxonMobil and Suncor under Colorado law for public and private nuisance, trespass, unjust enrichment and civil conspiracy, seeking damages for what they say climate change has cost them. They do not, the Colorado Supreme Court noted, “seek to enjoin any oil and gas operations or sales in Colorado or elsewhere.” On Monday the companies will ask the justices to end the case on the ground that federal law forbids it.

That is the question the companies asked: “Whether federal law precludes state-law claims seeking relief for injuries allegedly caused by the effects of interstate and international greenhouse-gas emissions on the global climate.” It is not the only question the Court will hear. When it granted review on 23 February, after the petition had been listed for five conferences since December, the Court added one of its own: “Whether this Court has statutory and Article III jurisdiction to hear this case.” Boulder’s brief puts it first. “This case should begin and end with jurisdiction,” it says.

What “final” means

The statute that lets the Court review state courts, 28 U.S.C. 1257(a), reaches “[f]inal judgments or decrees rendered by the highest court of a State.” The decision under review is not the end of anything in the ordinary sense. After a state trial judge refused to dismiss the suit, ExxonMobil asked the Colorado Supreme Court to step in under Colorado Appellate Rule 21, and Suncor joined. That court took the case, and on 12 May 2025 it held, five to two, that federal law does not preempt Boulder’s claims. It “discharge[d] the order to show cause” and sent the case back for further proceedings, expressing “no opinion on the ultimate viability of the merits.” Justice Samour, joined by Justice Boatright, would have made the order to show cause absolute and, in his words, “nip Boulder’s state-law claims in the bud.”

The companies’ brief offers two ways around the word “final”. The first is a 2020 decision, Atlantic Richfield Co. v. Christian, in which the Court reviewed a Montana Supreme Court ruling that had let a case go to trial, treating it as final because “[u]nder Montana law, a supervisory writ proceeding is a self-contained case, not an interlocutory appeal.” The Colorado opinion is captioned “Original Proceeding Pursuant to C.A.R. 21” and describes itself as an exercise of the court’s “original jurisdiction.” That, the companies say, makes it a separate case, and its end a final judgment. The second is the fourth category of exceptions the Court described in Cox Broadcasting Corp. v. Cohn in 1975, for state rulings that finally decide a federal issue where waiting “might seriously erode federal policy.”

Boulder’s brief says the label is not the thing. The companies “sought no writ of any kind, named no court as a respondent, requested ‘interlocutory review’ and reversal, and obtained a remand.” The Cox exception fails, it argues, because the companies still have other federal defenses to raise, and because a reversal would not end the case: Boulder could proceed under the law of the states where emissions occurred, or on emissions inside Colorado. If Cox lets the Court take interlocutory cases on policy grounds, Boulder says, “it should be overruled.” On Article III, it argues that a ruling which merely declined to dismiss a complaint inflicts no injury the Court can remedy, and that the costs of continuing to litigate do not count. The companies’ reply answers that the trial court “was a direct object of the order to show cause,” and that Boulder has asserted no claims based on “source-state law” or “in-state emissions” to fall back on.

The government’s two briefs

The United States has been here before, on the other side of the threshold. In December 2024, invited by the Court to give its views on a similar suit by Honolulu, the Solicitor General’s office told the justices that the Hawaii Supreme Court’s ruling did not fit the fourth Cox category and that “this Court therefore lacks jurisdiction under Section 1257(a) to review the Hawaii Supreme Court’s interlocutory decision.” It also said the Hawaii court had been “correct in concluding that the Clean Air Act does not categorically preempt” Honolulu’s claims. The Court denied review in January 2025; Justice Alito took no part.

In the Boulder case the government supports the companies. Its brief at the petition stage said that “after the change in Administration, the United States has reexamined its position” on the Clean Air Act and now considers such claims to conflict with it. On jurisdiction it stepped around Cox: “regardless of whether” the Colorado court could be deemed to have conducted interlocutory review for Cox purposes, it said, the decision was final because it ended an original proceeding under Rule 21. Its merits brief argues jurisdiction without citing Cox at all. The Colorado court’s description of its own proceeding as original, that brief says, “should be dispositive.” Boulder, for its part, adopts the reasoning of the government’s Honolulu brief on Cox. The government will have ten of the companies’ thirty minutes on Monday. Its motion for argument time is signed by a deputy, with a footnote: “The Solicitor General is recused in this case.” The motion also lists suits the United States has brought against Minnesota, New York and Vermont to block similar state-law liability.

Eight justices

On 28 September the Clerk of the Court wrote to counsel that “Justice Alito has determined that he will not continue to participate in this case.” The letter gives no reason. The Court’s dockets show he also took no part in the Honolulu petition and in the companies’ earlier, unsuccessful petition in the Boulder case in 2023; a Court spokesperson told NBC News in May that he had inadvertently recused in 2023, Colorado Public Radio reported. It added, citing a Consumer Watchdog report and his 2025 financial disclosures, that he holds investments in ConocoPhillips and Phillips 66, but no Suncor or ExxonMobil stock.

With eight justices, there are two ways the Court’s review could end without any ruling on preemption. A majority can hold that the Court lacks jurisdiction and dismiss. Or the justices can divide four to four, which would affirm the judgment by an equally divided Court and, as SCOTUSblog noted, would leave the Colorado decision in place. Boulder’s brief asks for either: “the Court should dismiss or affirm.”

What turns on the difference is the other suits. The companies count “nearly 60” state and local governments with similar claims; Colorado Public Radio put the number working through state courts at roughly two dozen. A dismissal for want of jurisdiction would say nothing about whether federal law bars any of them; Boulder’s case would go back to the trial court, and, as Boulder’s brief says, preemption “will remain reviewable after final judgment.” An affirmance by an equally divided Court sets no precedent either. Only a majority opinion on the merits would bind the courts hearing the others, and the companies’ own brief says that, left standing, the Colorado ruling “will constitute binding precedent in climate lawsuits pending in Colorado state courts.” Before any of that, five of eight justices have to agree that a ruling which sent a case back for trial was final.

Sources

The docket of No. 25-170 (including its entry of 28 September noting that Justice Alito “will not continue to participate in this case”), the questions presented, the companies’ opening and reply briefs, Boulder’s merits brief, the government’s petition-stage and merits briefs, its motion for divided argument and the Clerk’s letter of 28 September were read on the Supreme Court’s website. The Colorado Supreme Court’s opinion (2025 CO 21) was read as published by the Colorado Judicial Branch and in the petition appendix. The government’s December 2024 brief, the docket in Sunoco LP v. City and County of Honolulu, No. 23-947, and the docket of the companies’ 2023 petition, No. 21-1550, were read on the Supreme Court’s website. Atlantic Richfield and Cox Broadcasting are quoted as the briefs (including the government’s Honolulu brief, for Cox) quote them and were not read in full. The reported statement to NBC News, Justice Alito’s investments and the count of about two dozen suits are from Colorado Public Radio (28 September); the observation about a tie is from SCOTUSblog’s preview (1 October). The nearly 60 figure is the companies’ own. Amicus briefs were not read.