Before the U.S. Supreme Court heard arguments on Oct. 5 over whether federal law preempts local climate claims in Suncor Energy (U.S.A.) Inc. v. Board of County Commissioners of Boulder County, the justices confronted a threshold question: Do they have the legal authority to hear the case at all?
In an amicus brief supporting Boulder County and the City of Boulder, University of Colorado Law School Associate Professor Adam Sopko argued that the high court lacks statutory jurisdiction under 28 U.S.C. § 1257, which generally limits Supreme Court review of state court decisions to “final judgments.”
Because the underlying lawsuit has not yet gone to trial or reached a determination of liability, Sopko believes that Supreme Court intervention now would violate that final-judgment requirement and disrupt the traditional balance between federal and state courts.
The C.A.R. 21 Question
The dispute stems from a 2018 lawsuit filed by Boulder County and the City of Boulder against Suncor Energy and ExxonMobil in Colorado state district court. The municipalities asserted state common-law claims seeking damages for the costs of addressing local climate impacts, including wildfire mitigation, flood infrastructure repairs and road maintenance.
The energy companies moved to dismiss, arguing that federal common law and federal statutes preempt the municipalities’ state-law climate claims. The Boulder District Court rejected that argument.
Rather than proceeding toward discovery and trial, Suncor sought immediate review from the Colorado Supreme Court under Colorado Appellate Rule 21.
In May 2025, the Colorado Supreme Court held that the municipalities’ claims could proceed under state law and remanded the case to the district court for further proceedings. Suncor then petitioned the U.S. Supreme Court for certiorari.
When the high court granted certiorari in February, it took the unusual step of directing the parties to answer whether it has both Article III and statutory jurisdiction to hear the dispute.
Supervisory Power vs. Extraordinary Writs
The statutory question under 28 U.S.C. § 1257 turns in part on how federal law characterizes the Colorado Supreme Court’s C.A.R. 21 proceeding.
Sopko explained that Colorado’s high court draws its C.A.R. 21 authority from two provisions of Article VI of the Colorado Constitution: its original jurisdiction to issue traditional extraordinary writs and its general supervisory power over lower courts.
That distinction matters when determining whether the Colorado Supreme Court’s decision was final for purposes of federal review, Sopko said.
“When they’re using Section 3, they’re treating it like those old-timey writs,” Sopko said, referring to traditional remedies such as mandamus or prohibition, which are directed at an inferior court in circumstances involving an alleged legal error or other extraordinary circumstances.
Supervisory power via Section 2, by contrast, allows the state’s highest court to address significant or unsettled legal questions and provide guidance to lower courts.
Sopko holds that the Colorado Supreme Court acted under its supervisory authority in the Suncor decision. Suncor did not seek relief based on an immediate, irreparable injury from the trial court, and the Colorado Supreme Court’s 2025 opinion noted that the case presented an issue of significant public importance that had not previously been addressed.
Under § 1257 doctrine, Sopko said, an interlocutory ruling that resolves a legal question and sends a case back for trial is “virtually never a final judgment.”
The Atlantic Richfield Question
Suncor has pointed to the Supreme Court’s 2020 decision in Atlantic Richfield Co. v. Christian to support its argument that the Colorado Supreme Court’s decision is reviewable.
In Atlantic Richfield, the Supreme Court held that a Montana Supreme Court ruling issued through a state supervisory-writ proceeding was final (and therefore reviewable).
But in Colorado, Sopko said, Suncor invoked C.A.R. 21 to obtain an interlocutory review of a legal question in the ongoing case rather than pursuing a separate original action seeking a remedy against the lower court.
‘In a Word, Federalism’
For Sopko, the jurisdictional dispute reaches beyond the energy industry and the municipalities’ climate claims.
“In a word, federalism,” he said when asked about the stakes.
If the Supreme Court treats state supervisory decisions on preliminary motions as final judgments, he continued, it could make it easier for litigants to bring ongoing state-court cases before the U.S. Supreme Court before trial.
This could affect how state supreme courts use their supervisory authority to resolve important questions of state law, Sopko suggested, or state high courts could become more hesitant to exercise authority if doing so invites immediate federal review.
“It siphons off the ability of state courts to develop and apply their own state law,” he said. “That strikes at the heart of the autonomy and sovereignty of state judiciaries.”
If the Supreme Court concludes it lacks jurisdiction under § 1257, the lawsuit will return to Boulder County District Court for further proceedings.