Introduction 

Environmental governance in the United States (U.S.) has long been shaped by the balance between legislative, administrative, and judicial forces. Federal agencies such as the Environmental Protection Agency (EPA) have historically played a central role in translating broad statutes — such as the Clean Air Act — into actionable regulations, often relying on scientific expertise and technical knowledge to address complex environmental challenges. At the same time, courts have served as the decision-makers when it comes to statutory interpretation, determining the scope and limits of agency authority. Together, these institutions form the backbone of U.S. environmental and climate policies and regulations.

Two major legal developments are now reshaping this balance of power: the overturning of the Chevron Doctrine and the rollback of the 2009 Endangerment Finding. The Chevron Doctrine, established in 1984, required courts to defer to how different agencies interpret ambiguous statutes, thereby granting federal agencies like the EPA significant flexibility in implementing environmental laws. Its reversal in 2024 marks a fundamental shift, expanding judicial authority and reducing the powers previously given to agencies. In parallel, the 2009 Endangerment Finding, which established greenhouse gases as a threat to public health and welfare under the Clean Air Act, has served as the legal foundation for regulating greenhouse gas emissions across sectors. Its recent overturning undermines the federal government’s authority to regulate climate pollutants, creating uncertainty around the future of national climate and environmental policies.

This brief examines how institutional and legal changes shape the country’s capacity to respond to complex environmental challenges. Specifically, it analyzes how the redistribution of interpretive authority from agencies to courts, combined with the narrowing of EPA regulatory authority, affects federal, state, and local stakeholders. By tracing these developments through recent policy changes, including vehicle emissions standards and the National Environmental Policy Act (NEPA) and Council on Environmental Quality (CEQ) regulatory rollbacks, this brief analyzes their downstream consequences for federal, state, and local stakeholders and the implications for environmental governance, regulatory stability, and climate action in the United States.

Domestic Legal Shifts

Overturning of the Chevron Doctrine

What is the Chevron Doctrine?

The Chevron Doctrine is a principle of judicial review established by the Supreme Court in Chevron U.S.A., Inc. v. Natural Resources Defense Council, Inc., in 1984. The decision emerged during a period when Congress enacted broad regulatory statutes, such as the Clean Air Act, and increasingly relied on the scientific and technical expertise of federal agencies to implement them. As agencies took on a larger role in administering complex laws, courts repeatedly faced disputes over how much interpretive authority federal departments should have. The Chevron Doctrine provided a structured answer to that question.

Under this framework, courts generally defer to a federal agency’s reasonable interpretation of an ambiguous statute. Ambiguous laws are those that allow multiple reasonable interpretations due to vague terms, unclear definitions, contradictory provisions, hidden or unclear context, or numerical discrepancies. In practice, this meant that agencies such as the EPA had greater authority to interpret and implement broad statutory mandates enacted by Congress. Chevron deference operated through a two-step framework. First, a court asked whether Congress had directly addressed the issue. If the statute was clear, the court followed that meaning. If the statute was ambiguous, the court then asked whether the agency’s interpretation was reasonable. If the agency’s interpretation was reasonable, the court deferred to the agency rather than substituting its own interpretation.

Chevron was significant because many federal statutes, including environmental laws, contain broad or technical language that requires interpretation during implementation. In the environmental context, Chevron allowed agencies to apply scientific expertise and administrative judgment when carrying out statutes such as the Clean Air Act. More broadly, it shaped the balance of authority between courts and agencies by giving agencies interpretive flexibility where Congress had not spoken clearly.

For about 40 years, Chevron deference was the landmark principle in administrative law. However, the Supreme Court, in a 6-3 vote, overruled it in Loper Bright Enterprises v. Raimondo in June of 2024. By rejecting mandatory judicial deference, the Supreme Court shifted greater interpretive authority back to the courts. From an environmental policy perspective, this change may affect how federal agencies develop and defend regulations, how states respond to shifting federal authority, and how local governments and communities experience the practical consequences of regulatory uncertainty and legal change.

The End of Chevron Deference: Key Implications

The end of Chevron deference now means that judges are required to exercise independent judgment on a vast array of issues brought before the courts, ranging from environmental regulations to food safety standards. Agencies have lost the power to exercise their own authority and expertise in court rulings. This landmark decision impacts all federal agencies, including the EPA, the Federal Trade Commission, the Food and Drug Administration, and hundreds of others. Since 1984, more than 18,000 lower court cases have been decided based on Chevron deference grounds. Now, individuals, businesses, and organizations can challenge agency decisions.

Business law professionals explain that federal agencies can now expect more frequent legal challenges and closer scrutiny when interpreting ambiguous statutes, and courts can expect a heavier caseload. Legal expert Fernandez Lynch explained that relying on the courts for interpretation could result in conflicting and inconsistent decisions on regulations across circuits. This inconsistency can result in contradictory regulations that change from region to region across the country. Furthermore, conflicting interpretations could lead to more cases pushed to federal courts and a higher volume of requests for the Supreme Court. 

Legal experts further explain that lower courts will have to pass judgment on regulations in fields the judges may lack expertise in. This could increase the risk and cost for all regulated parties and could lead to an uncertainty tax on businesses, which means they will be more hesitant with their decision-making and increase costs in the face of uncertain political environments; these choices will be felt by American consumers. The decision will also make it easier for businesses and individuals to challenge regulations in court, with the potential to lead to an overall deregulation trend. This ruling works in corporate lobbying groups’ favor, providing a new tool to challenge regulations. In addition, U.S. taxpayers who challenge regulations could find courts more receptive to their arguments if the regulations do not represent the ‘best’ reading on a particular statute. As PwC explains in its policy brief, this could make it harder for the U.S. Treasury to adjust tax policy through regulations.

Shimon Anisfeld, Research Scientist at Yale, states, “This unfortunate SCOTUS decision shifts the responsibility for addressing these questions from EPA professionals to ill-equipped courts and will hamstring the EPA’s ability to protect water quality.” Todd Court of Yale Center for Business and the Environment adds that the ruling will make it difficult for regulators to maintain a baseline of performance expectation. However, since many large companies have to comply with regulations from countries outside of the U.S., they will likely have one approach to Environmental, Social, and Governance (ESG) practices. In addition, if certain practices result in harm, there is a threat of liability from other stakeholders. In other words, while the Chevron ruling is seen as negative, the Court argues that “it will not pull the rug out from ESG.” Other legal experts add that federal agencies are democratically accountable and have “broad-based ways to engage the public and elicit democratic input, like the notice and comment process through which agencies put out proposed regulations.”

Overturning of the 2009 Endangerment Finding

What is the Endangerment Finding?

In 1999, nineteen environmental, public interest, and trade organizations petitioned the EPA to issue rules for regulating greenhouse gases (GHGs) from new motor vehicles using Section 202(a)(1) of the Clean Air Act (CAA). Section 202(a)(1) of the CAA states that the EPA Administrator shall issue regulations for the emissions of “any air pollutant” from new motor vehicles or engines that can “reasonably be anticipated to endanger public health or welfare.” The petition placed great emphasis on the definition of “air pollutant” and “welfare,” which the CAA explicitly defines in Section 302(g) and Section 302(h), respectively. Welfare, as defined by the CAA, refers to weather and climate, among other factors affecting economic values, personal comfort, and well-being. 

In 2003, the EPA formally denied the request. The EPA cited four key reasons for denying the petition:

 

1. 1. The CAA was never intended to regulate GHGs, as evidenced by Congress’ multiple failed attempts at passing legislation to regulate GHGs.

1. 1. Section 202(a)(1) requires the EPA Administrator to issue regulations for air pollutants that, in their judgement, endanger public health or welfare. The EPA contested that the phrase “judgement” does not impose a mandatory duty but rather a discretionary or optional authority.

1. 1. Regulating GHGs from motor vehicles would interfere with fuel efficiency standards handled by the Department of Transportation, not the EPA.

1. 1. “The science of climate change is extraordinarily complex and still evolving,” and “there continue to be uncertainties in our understanding of the factors that may affect future climate change and how it should be addressed.”

Displeased with the federal agency’s decision, the petitioners appealed to the Court of Appeals for the District of Columbia Circuit for a judicial review of the EPA Administrator’s actions under Section 307(a)(1) of the CAA, which allows the DC Circuit to review any Administrator’s action with nationwide “scope or effect.” The court sided with the EPA. Following the decision by the DC Circuit, the petitioners, led by Massachusetts, appealed to the Supreme Court, culminating in the 5-4 decision Massachusetts v. EPA (2007) that ruled in favor of the petitioners and Massachusetts.

The Supreme Court ruled that the federal agency had improperly denied the petition, citing that Massachusetts had legal standing to sue due to the harm climate change posed to the state. Moreover, the court rejected the EPA’s argument that the CAA could not be used to regulate GHGs. Air pollutants, according to the majority court opinion, were defined broadly so the CAA could be applied for unconsidered future developments or emerging environmental factors at the time of the CAA’s passing. The majority opinion also maintained that the EPA can only avoid issuing regulations on GHGs if the agency is certain they do not contribute to climate change. Chief Justice Roberts’ dissenting opinion sided with the EPA, arguing that Massachusetts did not have legal standing in court because the state’s damages from climate change were uncertain and not individual or personal. Justice Scalia, who also delivered a dissenting opinion, argued the CAA was intended to combat conventional lower-atmosphere pollutants, not global pollutants like GHGs.

The landmark 2007 ruling pushed the EPA to develop its pivotal 2009 Endangerment Finding. Using Section 202(a) of the CAA, the 2009 finding lists six key globally persistent GHGs as threats to public health and welfare. While the finding itself doesn’t impose any regulatory requirements, it has been used as a prerequisite for implementing GHG emission standards for vehicles and even other sectors outside of the initial petition’s focus. A 2012 decision by the Court of Appeals for the District of Columbia Circuit expanded upon the Endangerment Finding by upholding the EPA’s GHG regulations on stationary sources like power plants, natural gas operations, and more.

On February 12, 2026, the EPA under the second Trump administration finalized a repeal of the 2009 Endangerment Finding, stating the federal agency has no authority under the CAA to regulate GHGs. The EPA’s reasoning for voiding the Endangerment Finding echoes the arguments initially brought forth by the agency in its 2003 decision. With the Endangerment Finding rescinded, vehicle and engine manufacturers no longer have an obligation to measure, report, or control GHG emissions, though this does not affect regulations on conventional air pollutants.

Key Implications of the Endangerment Finding’s Repeal

The overturning of the 2009 Endangerment Finding removes the federal obligation to regulate greenhouse gases. The Endangerment Finding also underpinned many regulations governing vehicle and power plant emissions. With a lack of regulatory oversight on industry, there could be a potential increase in fossil fuel emissions in the U.S. Additionally, the repeal of the Endangerment Finding could end federal grant programs aimed at reducing carbon emissions, which could also increase GHG emissions in the long run. 

With a lack of a national framework for GHG emissions, state-level authority becomes the primary driver for climate policy in the U.S., since they still retain the authority to regulate greenhouse gas-producing activities in their own state. Additionally, federal safeguards for power plants and oil companies may disappear because of the lack of federal authority over GHGs. Since GHGs were under federal jurisdiction, federal safeguards barred states and non-governmental organizations (NGOs) from suing power plants and oil companies for health and environmental damages linked to their GHG emissions. GHG emissions would no longer be regulated by the federal government, so federal safeguards would become void. In the long run, this would lead to states and NGOs having a greater chance of winning cases against fossil fuel-emitting companies. However, these lawsuits would only address damages that have already occurred. 

The EPA states that the repeal of the Endangerment Findings will support large and small businesses by reducing compliance costs related to emission regulations. As stated by Kelly Loeffler, the Administrator of the Small Business Administration, “EPA’s reconsideration of the endangerment finding will eliminate burdensome regulations and save small businesses at least $170 billion.” Additionally, repealing the findings can reduce the price of non-electric vehicles, as regulatory requirements to monitor and comply with emission standards for motor vehicles would no longer be legally necessary. However, others argue that U.S. citizens would actually save money under the Endangerment Findings, as, in the long run, individuals could avoid the financial burden of climate change-related health issues. 

The repeal of the Endangerment Findings can increase the risk of climate change in the future, as there will be a greater amount of unregulated GHG emissions in the U.S. In the long run, this can affect U.S. citizens, as climate change harms crop growth and increases food prices within the nation. Furthermore, climate change can increase natural disasters by rising sea levels and increasing atmospheric temperature. These disasters, like intense hurricanes and windstorms, can cause major mental and physical trauma to U.S. citizens who are impacted by those events, as well as potential health issues. However, Supreme Court Justice Scalia argued that the Clean Air Act was not intended to combat global climate change, so any health-related impacts caused by climate change are outside of the restrictions of the Clean Air Act and the Endangerment Findings.   

From Legal Shifts to Policy Rollbacks: Mini Case Studies

Vehicle Emission Standards Rollback

The EPA has used the 2009 Endangerment Finding as a prerequisite for enacting regulations on vehicular GHG emissions. In 2010, the EPA, in collaboration with the National Highway Traffic Safety Administration, jointly finalized the first GHG emission standards, establishing average GHG and fuel economy standards for model year 2012-2016 vehicles:

	Baseline (Model Year 2011)	Target (Model Year 2016)
CO2 Emissions	295 grams/mile	250 grams/mile
Fuel Economy Standard	27.6 miles per gallon	34.1 miles per gallon

Note: Data on 2011 baseline CO₂  emissions is unavailable. The 2011 data presented for CO₂ represents the EPA’s CO₂ target for 2012 model year vehicles.

By 2016, the EPA not only met its vehicular GHG emission reduction goals but exceeded them. In 2012, the motor industry exceeded CO₂ reduction targets by over 11 grams/mile, and in 2013, exceeded the target by 12 grams/mile. Vehicular GHG emission standards have been revisited and made more stringent over time. Most recently, in 2024 under the Biden Administration, the EPA developed “more protective final standards to further reduce harmful air pollutant emissions” from vehicles with the intention of reducing smog, climate pollution, and fuel and maintenance costs.

The consequence of rolling back emission regulations means that all federal GHG emission standards for vehicles (model years 2012–2027 and beyond) and off-cycle credits were terminated. Off-cycle credits are government incentives given to auto manufacturers to include eco-friendly technologies, like the “stop-start feature”, into their vehicles. 

The lack of emission standards can decrease car prices for consumers, as there will be fewer federal hurdles in the creation of gasoline cars. Stakeholders also state that these rollbacks will allow manufacturers to align with consumer demands for a variety of affordable vehicles. However, others argue that gas prices could increase as a result of the emissions standards rollback. This is because, as vehicle prices decrease, more consumers will buy those vehicles, and the demand for gas will increase. 

Although government rollbacks may reduce incentives for electric-vehicle manufacturing in the U.S., the domestic market is unlikely to deviate from electric or hybrid vehicles immediately. This is because deviating from clean, fuel efficiency technologies could harm U.S. manufacturers’ export sales and limit their profits in the global vehicle markets. 

Passenger cars and trucks contribute to over half of transportation CO2 emissions. Since federal vehicle emissions standards were terminated, these GHG emissions can rise into the atmosphere and lower air quality in the long run. This lower air quality can harm the health of U.S. citizens by increasing the risk of diseases like asthma and cancer. Additionally, releasing more greenhouse gases into the atmosphere increases temperatures worldwide. This can greatly harm the U.S. environment in the long run by increasing natural disasters, limiting viable habitats for native U.S. species, and increasing the risk of extinction for those species. 

National Environmental Policy Act (NEPA) and Council on Environmental Quality (CEQ) Regulatory Rollbacks

The 1969 implementation of the National Environmental Policy Act (NEPA) has historically depended on the interpretive authority of the Council on Environmental Quality (CEQ), which issues regulations and guidance to federal agencies on conducting environmental review. For decades, this interpretive role was reinforced by the Chevron Doctrine, under which courts deferred to reasonable agency interpretations of ambiguous statutory provisions. This allowed CEQ to shape key elements of NEPA practice.

Recent legal challenges and the broader rollback of Chevron deference have significantly altered this dynamic. Without mandatory judicial deference, courts are now more willing to independently interpret NEPA’s statutory language, thereby limiting CEQ’s ability to define how the law is applied in practice. This shift is illustrated by cases such as the 2022 Wild Virginia v. Council on Environmental Quality, in which plaintiffs challenged CEQ’s authority to revise NEPA regulations, reflecting a broader trend of increased judicial scrutiny over agency rulemaking and guidance, particularly when agencies attempt to expand or reinterpret their regulatory scope.

The rollback of NEPA regulations and the shifting role of CEQ indicate changes in how environmental policy is interpreted and implemented. These changes may weaken the federal government’s ability to maintain consistent environmental review standards. A 2025 Bipartisan Policy Center roundtable found that the current NEPA framework is already viewed as “too slow and unpredictable,” and that reforms to judicial review and permitting processes could significantly alter how federal agencies conduct environmental assessments. As CEQ’s role becomes more constrained, federal agencies may rely less on consistent federal guidance and more on case-specific interpretations in environmental review practices.

Reduced federal clarity also shifts greater responsibility to state and local governments, which will likely increase variation in environmental governance across jurisdictions. Research on NEPA implementation shows that environmental review processes are often shaped by institutional interpretation and administrative practice, which can differ significantly when consistent federal regulation weakens. As a result, state and local stakeholders may adopt divergent approaches or rely on their own environmental review frameworks, which could lead to a more fragmented regulatory landscape.

NEPA has already become one of the most frequently litigated environmental statutes, which creates what some describe as a “litigation cycle” that delays projects and increases uncertainty. As judicial involvement grows, project developers, communities, and other stakeholders may face longer approval timelines and higher legal costs. This shift suggests that environmental outcomes may increasingly depend on litigation rather than predictable administrative procedures, which will make the process less transparent and more difficult for individuals to navigate.

Conclusion 

Legal and regulatory changes have reshaped environmental governance in the U.S. The overturning of the Chevron Doctrine shifts interpretive authority from federal agencies to the courts, while the rollback of the 2009 Endangerment Finding removes a key legal foundation for federal climate regulation. These changes increase the role of judicial interpretation in shaping policy outcomes, limit federal agencies’ reliance on technical expertise, and make it more difficult for the federal government to regulate greenhouse gas emissions and to maintain consistent regulatory standards.

With reduced federal authority, existing laws and regulations that once relied on judicial deference to agency interpretations are more open to challenge and reinterpretation. The rescinding of the Endangerment Finding leaves states to set their own policies, making state and local governments likely to take on a larger role in environmental governance, which can result in greater variation across jurisdictions. While businesses may face lower compliance costs, these changes also increase uncertainty and shift greater reliance on litigation. For individuals, the long-term consequences may include increased exposure to climate-related risks. Overall, environmental governance is likely to become less predictable and increasingly shaped by courts and state-level action than by coordinated federal regulation.

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