Boulder County and the City of Boulder seek damages from Suncor Energy and ExxonMobil in Colorado state court, alleging the companies contributed to climate change harms while misleading the public. The Colorado Supreme Court held that the Clean Air Act does not preempt the claims, and the U.S. Supreme Court agreed to review that ruling. The Court heard argument on October 5, 2026, as the first case of its October 2026 term.
Latest development Oct 5, 2026
On October 5, 2026, the U.S. Supreme Court heard oral argument on whether federal law precludes Boulder’s state-law damages claims and whether the Court has jurisdiction to hear the case. The Solicitor General shared the companies’ argument time as amicus curiae. Justice Samuel Alito did not participate.
Why it matters
The U.S. Supreme Court will decide whether federal law forecloses state-law damages suits over interstate and international greenhouse gas emissions. The answer will affect roughly two dozen similar suits that states, counties, and cities have brought against oil and gas companies.
Background
On April 17, 2018, Boulder County, San Miguel County, and the City of Boulder sued Suncor Energy and ExxonMobil in Colorado state court. The local governments seek damages under state tort law for the costs of adapting to climate change, including heat waves, wildfires, drought, and flooding. They attribute those costs to the companies’ fossil fuel production and to decades of alleged deception about its climate effects. San Miguel County’s claims were later severed for improper venue and proceed separately in Denver District Court.
The companies removed the case to federal court, which began a five-year jurisdictional fight. In September 2019, the U.S. District Court for the District of Colorado rejected every ground for removal and sent the case back to Boulder County District Court. The U.S. Court of Appeals for the Tenth Circuit affirmed in July 2020. In May 2021, the U.S. Supreme Court vacated that judgment and remanded in light of BP p.l.c. v. Mayor of Baltimore. The Tenth Circuit again held in February 2022 that the case belongs in state court, and the Supreme Court denied review in April 2023.
Back in state court, Suncor and Exxon argued that the Clean Air Act and related federal law displace or preempt Boulder’s public nuisance, trespass, unjust enrichment, and civil conspiracy claims. They contend that the alleged harm flows from interstate and international greenhouse gas emissions, which only Congress and federal regulators can govern. On May 12, 2025, the Colorado Supreme Court rejected that argument by a 5–2 vote and held that the claims may proceed under state law. The case returned to the district court for further proceedings on the merits. It is the lead vehicle for roughly two dozen similar climate damages suits that states, counties, and cities have brought against oil and gas companies across the country.
After Suncor and Exxon petitioned on August 8, 2025, the U.S. Supreme Court granted certiorari on February 23, 2026, on whether federal law precludes the state-law damages claims. On February 27, 2026, the Court added a second question: whether it has statutory and Article III jurisdiction to hear the case. On September 4, 2026, the Court granted the Solicitor General’s motion to argue as amicus curiae in support of the companies, splitting argument time with their counsel. On September 28, 2026, the Court notified the parties that Justice Samuel Alito would not participate in the case. The Court heard oral argument on October 5, 2026, as the first case of its October 2026 term.
Timeline 15 events
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HearingSupreme Court hears oral argument on preemption and jurisdiction
The case was the first argument of the Court’s October 2026 term.
US Supreme Court Sets Climate Suit for First Case of Next Term
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OrderJustice Alito recuses from Suncor v. Boulder
The Supreme Court notified the parties that Justice Samuel Alito would not participate in the case, days before oral argument.
Justice Alito Recuses From Supreme Court Suncor Climate Case (1)Samuel Alito recuses from Suncor v. Boulder climate liability caseJustice Samuel Alito recuses from major climate case Suncor v. BoulderSupreme Court's Samuel Alito Recuses Himself From Suncor Energy Climate CaseJustice Alito Says Recusal in Suncor Energy v. Boulder County a "Difficult Judgment Call"
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OrderSupreme Court grants the Solicitor General divided argument time
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OrderSolicitor General moves to argue as amicus supporting Suncor and Exxon
The Solicitor General asked to share the companies’ argument time. The Court granted the motion on September 4, 2026.
Motion of the United States for Leave to Participate in Oral Argument
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OrderExxon Mobil Corporation amends Supreme Court corporate disclosure statement
Exxon’s counsel told the Court that, after a July 2026 redomiciliation, Exxon Mobil Corporation is now a wholly owned subsidiary of ExxonMobil Holdings Corporation. The new holding company trades under ticker XOM.
Amended Corporate Disclosure Statement letter, No. 25-170Suncor Energy Inc. v. County Commissioners of Boulder County (25-170)ExxonMobil Holdings Name to Debut as Company Moves Headquarters to Texas - BloombergExxonMobil Holdings Corp - Form 8-K12B - FY2026ExxonMobil Completes Redomiciliation and Holding Company Transition - The Globe and Mail
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OrderSupreme Court adds jurisdictional question for briefing
The Court directed the parties to brief and argue whether it has statutory and Article III jurisdiction to hear the case. That question is in addition to the preemption question in the cert petition.
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OrderU.S. Supreme Court grants certiorari
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AppealSuncor and ExxonMobil petition the U.S. Supreme Court for certiorari
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JudgmentColorado Supreme Court holds Clean Air Act does not preempt claims
The court ruled 5–2 that Boulder’s state-law claims may proceed.
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OrderSupreme Court denies certiorari on removal jurisdiction
The U.S. Supreme Court denied Suncor and Exxon’s petition seeking review of the Tenth Circuit’s affirmance of the remand order, allowing the case to proceed in Boulder County District Court.
Supreme Court Denied Fossil Fuel Companies' Requests for Certiorari on Jurisdictional Issues
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AppealTenth Circuit again holds case belongs in state court
On remand, the Tenth Circuit again ruled that the case should proceed in Colorado state court rather than federal court.
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OrderSupreme Court vacates and remands in light of BP v. Baltimore
The U.S. Supreme Court granted certiorari and vacated the Tenth Circuit’s judgment. It remanded for reconsideration of additional removal grounds in light of BP p.l.c. v. Mayor of Baltimore.
Board of County Commissioners of Boulder County v. Suncor Energy (U.S.A.), Inc.
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AppealTenth Circuit affirms remand to state court
The Tenth Circuit affirmed the district court’s remand order. It held that it lacked jurisdiction to review most of the asserted grounds for removal.
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OrderFederal district court remands case to Colorado state court
Judge William J. Martinez of the U.S. District Court for the District of Colorado rejected all grounds for removal asserted by Suncor and Exxon. The court sent the case back to Boulder County District Court.
Board of County Commissioners of Boulder v. Suncor Energy (U.S.A.) Inc.
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FilingColorado local governments sue Suncor and ExxonMobil in state court
Boulder County and the City of Boulder sued alongside San Miguel County, whose claims were later severed for improper venue and proceed in Denver District Court. Only Boulder County and the City of Boulder are parties to the Supreme Court case.
Experimental AI forecast
How it is madeHow will the U.S. Supreme Court resolve Suncor Energy v. Boulder County (No. 25-170) by July 31, 2027?
- Court bars Boulder’s state-law claims50%
- Court lets Boulder’s claims proceed20%
- Court dismisses for lack of jurisdiction14%
- Vacated and remanded on narrower ground13%
- Still pending on July 31, 20273%
- Resolves by
- Jul 31, 2027in 9 months
- Record confidence
- Medium
The most likely outcome, at 50%, is that the Supreme Court holds federal law bars Boulder’s state-law climate damages claims by July 2027. The grant itself, the Court’s usual reversal rate, and the Solicitor General’s support favor the companies. An eight-member Court and an added jurisdictional question leave real room for other results.
How it resolves. Resolves on the Supreme Court’s disposition as shown on its docket and in its opinion or order. “Bars claims” if the Court holds federal law precludes Boulder’s state-law damages claims and reverses. “Claims proceed” if the Court affirms the Colorado Supreme Court on the merits or by an equally divided Court. “Dismissed” if the Court dismisses for lack of jurisdiction or as improvidently granted. “Vacated and remanded” if the Court vacates on a narrower ground without deciding whether federal law bars the claims. “Still pending” if no disposition issues by July 31, 2027.
Reasoning
Starting point. U.S. Supreme Court merits cases granted on a petitioner’s request, with the Solicitor General supporting the petitioner: The Court reverses or vacates in roughly 70% of argued cases. Petitioners backed by the Solicitor General as amicus win somewhat more often.
The Court reverses or vacates about 70% of the cases it hears, and the Solicitor General’s support for the companies adds weight to reversal. The 5–2 Colorado Supreme Court ruling is the judgment under review. Twenty-six states support the companies as amici. The Court’s own addition of a jurisdictional question matters. The Colorado ruling came before any trial, so whether it is a reviewable final judgment is open, and dismissal remains a live path. A vacatur on a narrower ground, such as a limited preemption holding with remand, is also plausible. Alito’s September 28, 2026, recusal moved claims proceed up five points and bars claims down five, because an eight-member Court can affirm by an equal division. Such an affirmance would let the claims go forward without setting precedent. The leading alternative to a ruling for the companies is a disposition that leaves the Colorado judgment standing, through affirmance, an equally divided vote, or a jurisdictional dismissal. A decision is expected by late June or early July 2027 because argument opens the term, so still pending is unlikely.
Solicitor General supports the companies as amicus · Added question on Supreme Court jurisdiction over interlocutory ruling · Eight-member Court allows affirmance by equal division · High reversal rate in granted Supreme Court cases · Outcome governs roughly two dozen similar climate suits
Generated automatically by Claude Opus 5.5 on Oct 2, 2026 from this case’s record on this site, and published without editorial review. The probabilities are the model’s judgment, not measured frequencies, and they are scored publicly as cases resolve. Not legal or investment advice. How the forecasts are made
What it would mean
If the Court holds that federal law bars Boulder’s claims, the 50% outcome, Exxon Mobil and Suncor would owe Boulder nothing and the suit would end. The holding would bind state courts hearing the dozens of similar climate damages suits brought by states and cities. It would also strengthen challenges to state climate superfund laws, such as New York’s $75B program, which a federal trial court has already struck down. For the companies, the main gain is an end to defense costs and to an open-ended liability across many forums.
If the Court lets the claims proceed, the 20% outcome, no money would move soon. The case would return to Boulder County District Court for discovery and trial. Cash would change hands only after a verdict and further appeals. Boulder’s own 2018 study put county adaptation costs through 2050 at about $96M to $160M, small beside Exxon Mobil’s market value of about $670B. The larger consequence is the signal it would send to dozens of parallel suits that together seek potentially billions of dollars, with insurance coverage unlikely to absorb it.
Money, who pays, markets and what to watch
Two steps ahead. With Justice Alito out, a 4–4 split would affirm the Colorado ruling without setting precedent. That result, like a jurisdictional dismissal or a narrow remand, would let Boulder go forward while leaving other courts free to rule the other way. The companies could return to the Court after a final judgment, so a narrow loss would buy them time rather than end the fight. Plaintiffs’ settlement leverage would rise only with a merits ruling in their favor.
The money
- Exxon Mobil: up to $157M. Boulder County’s 2018 commissioned study estimated adaptation costs for only some climate effects across the county through 2050 at $96M to $157M. The complaint does not state a figure. Low is zero if liability is not found or is allocated to Suncor. High assumes Exxon Mobil bears the full estimate. This is the same pool of claimed costs as the Suncor row, not an additional amount. Only if the claims survive the Supreme Court and Boulder then wins at trial and on appeal. That is years away. Nothing moves if the Court bars the claims.[1][2] That is up to 0.02% of its market value ($669.4B, Sep 17, 2026), and up to 0.05% of its annual revenue ($323.9B, 2025), and up to 1.1% of its cash ($13.8B, Sep 30, 2025).
- Suncor Energy: up to $157M. Same Boulder County 2018 estimate of $96M to $157M in adaptation costs through 2050, claimed against the three Suncor entities and Exxon Mobil together. Low is zero if liability is not found or is allocated to Exxon Mobil. High assumes the Suncor entities bear the full estimate. This is not additive to the Exxon Mobil row. Only after a trial verdict in Boulder County District Court and appeals. Nothing moves if the Court bars the claims.[1][2] That is up to 0.2% of its market value ($77.1B, Aug 2026).
- Figures used: Exxon Mobil, market value $669.4B (Sep 17, 2026)[3] · Exxon Mobil, annual revenue $323.9B (2025)[4] · Exxon Mobil, cash $13.8B (Sep 30, 2025)[5] · Suncor Energy, market value $77.1B (Aug 2026)[6]
Who pays
- The named payers are Exxon Mobil and three Suncor entities, including Canadian parent Suncor Energy Inc. Any damages would fall on them. How liability would be split between them has not been determined.[2]
- Insurance is unlikely to cover much. In Aloha Petroleum v. National Union, the Hawaii Supreme Court held in 2024 that greenhouse gases are pollutants under standard pollution exclusions in general liability policies. AIG units prevailed in that case.[7][8]
- If the claims are barred, Boulder’s taxpayers keep the adaptation costs. The county’s 2018 study put them at $96M to $157M through 2050 for only some climate effects.[1][9]
- Exxon Mobil generated $52.0B in operating cash flow in 2025. Defense costs and any eventual award could be paid from operations without outside financing.[10]
Markets
- Exxon Mobil trades on the New York Stock Exchange as XOM. Its market value was about $669B on September 17, 2026.[3]
- Suncor Energy trades in Toronto and New York as SU. Its Toronto market value was C$113.47B on September 24, 2026, up from C$73.49B at the end of 2025.[11]
- No share-price move has been attributed to the May 12, 2025 Colorado Supreme Court ruling or the February 23, 2026, certiorari grant. Oil prices and earnings have driven both stocks.[3][11]
- The insurers that write general liability coverage for energy companies have a stake in the outcome. The Aloha ruling makes defense and indemnity claims from climate suits easier for them to resist.[8]
Collecting
- No judgment exists yet. If the claims survive, cash could move only after trial in Boulder County District Court and appeals through the Colorado courts. A second trip to the U.S. Supreme Court is possible.[12]
- Both defendants are solvent and operate in the United States, so a final Colorado judgment would be enforced in U.S. courts without any foreign recognition step. Exxon Mobil held $13.8B in cash on September 30, 2025.[5]
- The Canadian parent, Suncor Energy Inc., is itself a named defendant. Boulder would not need to pierce a corporate veil to reach it.
Beyond the parties
- This is the first time the Court will decide whether federal law bars climate damages suits. A merits ruling would govern dozens of similar state and local suits against energy companies.[13][12]
- A ruling for the companies could also weaken state climate superfund laws. In September 2026, a federal trial court struck down New York’s law, which sought $75B over 25 years. Vermont’s similar law now faces the same question.[14][15][13]
- If the claims proceed, other Colorado governments could bring similar suits. The Colorado Fiscal Institute projects that climate impacts will cost Coloradans up to $37B from 2025 to 2050.[16]
- The Solicitor General’s support for the companies puts the federal government against state-law climate liability. That position would carry into the parallel cases however the Court rules.
What to watch
- Oct 5, 2026Supreme Court hears argument on preemption and jurisdiction in Suncor v. Boulder[12]
- PendingCourts weigh Vermont’s climate superfund law after New York’s law was struck down[15][14]
- PendingSan Miguel County’s severed climate suit advances in Denver District Court
Sources
- The Impact of Climate Change: Projected Adaptation Costs for Boulder County, Colorado assets.bouldercounty.gov · 2018-04
- The court’s coming climate-change case and the very confused doctrine of preemption scotusblog.com · 2026-09
- ExxonMobil Holdings (XOM) Market Cap & Net Worth stockanalysis.com · 2026-09-17
- ExxonMobil Holdings (XOM) Revenue stockanalysis.com · 2026
- ExxonMobil Announces Third-Quarter 2025 Results investor.exxonmobil.com · 2025-10-31
- Suncor Energy (SU) - Market capitalization companiesmarketcap.com · 2026-08
- Aloha Petroleum Ltd v. National Union Fire Insurance Company of Pittsburgh PA (2024) caselaw.findlaw.com · 2024
- AIG Units Notch Win in Hawaii Court Over Climate Change Coverage news.bloomberglaw.com · 2024
- Colorado Supreme Court advances historic Boulder climate accountability case bouldercolorado.gov · 2025-05
- ExxonMobil Announces 2025 Results investor.exxonmobil.com · 2026-01-30
- Suncor Energy (TSX:SU) Market Cap & Net Worth stockanalysis.com · 2026-09-24
- The Legal Planet Guide to Suncor Energy v. County Commissioners of Boulder County legal-planet.org · 2026-09-08
- Climate Change and State Authority: Potential Broad Implications of the Supreme Court’s Grant of Certiorari in Suncor Energy v. Commissioners of Boulder County bdlaw.com · 2026-02
- Federal Judge Strikes Down New York’s Climate Change Superfund Law insideclimatenews.org · 2026-09-01
- New York Climate Superfund Rulings Put Vermont Law in Focus gravel2gavel.com · 2026-09-30
- SCOTUS to hear Boulder’s case against Suncor, setting a precedent for climate change cases 9news.com · 2026
Experimental AI analysis by Claude Opus 5.5 on Oct 2, 2026, built on the forecast above from this case’s record and public sources found by the model’s own web search. Figures are estimates as of the dates shown, and shares of value are computed by the site from the figures cited. Published without editorial review. Nothing here predicts the price of any security or is investment advice. How it is made