On November 25, 2025, Suncor Energy (U.S.A.) Inc., Suncor Energy Sales Inc., and Exxon Mobil Corporation filed their reply brief in support of their request for U.S. Supreme Court review of the Colorado Supreme Court’s May 2025 opinion holding that federal law did not preempt state law claims brought by the City of Boulder and the County Commissioners of Boulder County seeking to hold the companies liable for climate change-related injuries. The companies argued that the question presented—whether federal law precludes the plaintiffs’ state-law claims—“cries out for the Court’s resolution.” The companies contended that the court had constitutional and statutory jurisdiction, that the Colorado Supreme Court’s decision was incorrect and deepened a conflict on the question presented, and that “further percolation” of similar cases in state courts “would provide no benefit.” The case was distributed for the Court’s December 12 conference.

Action by Colorado local governments seeking damages and other relief from fossil fuel companies for climate change harms.

Suncor Energy (U.S.A.) Inc. v. County Commissioners of Boulder County

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Briefing Completed on Fossil Fuel Companies’ Certiorari Petition in Boulder Climate Case

Filed

United States of America

Colorado

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An aim to achieve a quantifiable outcome within a given time-frame, set by an institution such as a national government.

Policy instruments are techniques or tools used by governing authorities to promote certain policies in order to achieve predetermined goals. Put simply, instruments are how a government tries to achieve its goals, with this taxonomy being focused on national policy instruments.

Risk is the potential for adverse consequences resulting from the dynamic interplay between (climate-related) hazards, exposure, and vulnerability of affected human or ecological systems.

Groups  of people who are adversely affected by climate change or the response to it

A set of principles, processes, and practices that build economic and political power to shift from an extractive economy to a regenerative economy.

Justice is the ethical and political framework that addresses fairness, including issues of responsibility, rights, and structural inequity.

Renewable energy means all forms of energy produced from renewable sources in a sustainable manner.

Fossil fuel is a generic term for non-renewable energy sources such as coal, fossil gas, and oil (including crude oil, and petroleum products), that can be used for electricity and heat generation. Fossil fuels are hydrocarbons formed from pressurised and heated organic material buried over millions of years.

Molecules in the atmosphere that play a key role in the greenhouse effect by trapping heat radiating from Earth’s surface.

Area of the economy in which actors engage in identical or related activities.

In human systems, the process of adjustment to actual or expected climate change and its effects, in order to moderate harm, increase resilience or exploit beneficial opportunities. In natural systems, the process of adjustment to actual climate change and its effects; human intervention may facilitate adjustment to expected climate change and its effects.

The management and allocation of funds, assets and investments to meet various objectives

A ban is a legal action that prevents the sale or supply of a product or service, or that recalls a product from the market. Examples are bans on SF6, greenwashing, fossil fuel advertisement or single-use plastics.

A financial institution that manages a country's currency and can promote climate-related initiatives through green monetary policy and other means.

Fossil gas, commonly known as natural gas, is a fossil fuel consisting chiefly of methane with smaller amounts of other hydrocarbons and trace gases, found in underground deposits.

Any compulsory, unrequited payment to the government levied on corporations or individuals. This can be for environmental reasons, such as introducing a Carbon tax to set a price that emitters must pay for the greenhouse gases they emit.

The activities of industries involved in the production, distribution, and sale of energy, including electricity, gas, and renewables.

This sector involves the wholesale and retail selling of goods.

This sector creates and distributes information and entertainment through television, radio, print, and digital platforms.

Activities of government agencies and institutions that provide public services, enforce laws and manage public resources.

Briefing Completed on Fossil Fuel Companies’ Certiorari Petition in Boulder Climate Case

Policy instrument

Fossil fuel

Greenhouse gas

Economic sector

Finance