On February 12, 2026, the U.S. Environmental Protection Agency (EPA) issued a long-anticipated rule repealing the 2009 “Endangerment Finding.” The 2009 finding concluded that six key greenhouse gases (GHGs), including carbon dioxide and methane, endanger public health and welfare. For the past 17 years, the 2009 Endangerment Finding has served as the legal foundation for federal regulation on vehicle emissions and stationary sources. As issued by the Trump EPA, the repeal of the 2009 Endangerment Finding eliminates a range of federal GHG emission standards for motor vehicles, plus sets the stage for rescinding other GHG regulatory programs. The Trump EPA argues that repealing the 2009 finding will reduce regulatory costs by more than $1 trillion, while increasing consumer choice and easing what it described as burdensome federal mandates. To fully appreciate the significance of the 2009 Endangerment Finding, it is necessary to revisit the landmark U.S. Supreme Court case that set the current GHG regulatory framework in motion.
The Supreme Court Decision That Shaped GHG Regulation
On April 2, 2007, in Massachusetts v. EPA, 549 U.S. 497 (2007), the U.S. Supreme Court ruled that GHGs fall within the definition of “air pollutant” under the Clean Air Act (Act) and therefore, may be regulated by the EPA. The Court further ruled that before regulating GHG emissions from new motor vehicles, the EPA must determine whether those vehicle emissions may “reasonably be anticipated to endanger public health or welfare,” consistent with Section 202(a) of the Act.
The central issue in the case was whether the EPA had statutory authority to regulate GHG emissions from new motor vehicles. Because the Act was originally adopted to address local and regional air pollution, not global climate change, the Act does not specifically reference greenhouse gases. As a result, the Court was required to interpret whether GHGs fall within the Act’s broad definition of “air pollutant.”
A coalition of states led by Massachusetts, along with several cities and environmental organizations, brought suit against the EPA under the Bush Administration after the agency declined to regulate carbon dioxide and other GHGs. The EPA argued that it lacked statutory authority under the Clean Air Act and further, that scientific uncertainty justified its decision not to regulate. In a 5–4 decision, the Court rejected those arguments and concluded that greenhouse gases qualify as “air pollutants” under the Act. The Court also directed the EPA to determine, based on science, whether GHG emissions from new motor vehicles endangered public health or welfare pursuant to Section 202(a). Based on its analysis, if EPA determines there is “endangerment” to the public health or welfare, then EPA is legally obligated to regulate GHG emissions under the Act.
As a result, this U.S. Supreme Court decision has since played a central role in shaping U.S. climate policy and regulation. On December 7, 2009, under the Obama Administration, the EPA issued its formal determination, now commonly known as the 2009 Endangerment Finding, concluding that certain greenhouse gases do endanger public health and welfare. Subsequently, the 2009 Endangerment Finding was later upheld on appeal by the U.S. Court of Appeals for the D.C. Circuit in a decision issued on June 26, 2012. The ruling in Massachusetts v. EPA is now widely regarded as a pivotal moment in U.S. environmental law, which established the legal basis for federal regulation of greenhouse gas emissions from mobile and stationary sources.
The Road Ahead for Climate Regulation – Litigation, Uncertainty and Fallout
Formally repealing the 2009 Endangerment Finding not only rescinds the motor vehicle GHG standards that relied on it but also clears the way for the Trump EPA to roll back greenhouse gas regulations affecting stationary sources and other sectors, including power plants and the oil and gas industry. However, the path forward is unlikely to be smooth.
In support of its repeal, the Trump EPA asserts the prior finding was based on a “profound misreading” of the U.S. Supreme Court’s 2007 decision in Massachusetts v. EPA. The agency now advances a revised interpretation of Section 202 of the Clean Air Act, arguing that the term “air pollutant” should be understood in relation to harms from local or regional exposure, rather than global effects. According to the Trump EPA, this interpretation better reflects the ordinary meaning of “air pollutant” at the time the Clean Air Act was enacted, as well as the statute’s structure, legislative history, and the agency’s pre-2009 regulatory practice. Among other arguments, the Trump EPA also claims there is scientific uncertainty regarding the actual harms to public health that can be linked to greenhouse gas emissions.
The repeal is expected to trigger significant litigation. Within days of its issuance, on February 18, 2026, climate and public health advocates filed a Petition for Review in the U.S. Court of Appeals for the D.C. Circuit in American Public Health Association, et al. v. EPA. That filing likely marks the beginning of a multi-year legal battle that could unfold across multiple fronts. Once again, this dispute could eventually reach the U.S. Supreme Court, potentially prompting a reconsideration or clarification of its 2007 landmark decision in Massachusetts v. EPA.
This renewed litigation over greenhouse gases is also likely to create uncertainty for regulated industries. Although business interests often favor deregulation, some industry groups in this instance may align with environmental advocates, as the repeal is expected to create regulatory instability and possibly jeopardize capital investments previously made to comply with now-repealed requirements. Moreover, a future EPA administration could reverse course again on greenhouse gas regulation, or state-level climate regulation may intensify in response, forcing affected industries to reinvest additional capital and comply with even more stringent standards.
Conclusion – A Defining Moment for Climate Regulation
In sum, the repeal of the 2009 Endangerment Finding marks a pivotal shift in federal climate policy with consequences that extend well beyond vehicle emissions standards. By challenging the legal and scientific foundation established after Massachusetts v. EPA, the Trump EPA has set the stage for renewed judicial review of its regulatory authority, and the courts will again be asked to define the limits of federal jurisdiction over greenhouse gases. At present, there is a 6 – 3 conservative majority on the U.S. Supreme Court, which could ultimately favor the Trump EPA in its efforts to permanently roll back federal GHG regulations of any kind. Regardless, it may be several years before these legal disputes are resolved, which leave regulated businesses facing an uncertain future and a potentially fragmented regulatory landscape as states look to fill the gap. While this repeal may provide short-term federal regulatory relief, it is expected that state requirements, market expectations, customer demands, and investor scrutiny of GHG emissions will continue to shape climate-related strategic business decisions for the foreseeable future.
As federal climate regulation becomes more uncertain and market pressures intensify, proactive compliance and strategic planning are critical. Trinity’s compliance and sustainability teams help companies assess regulatory exposure, maintain compliance, and position their operations for resilience in a rapidly evolving climate policy environment. For more information on Trinity’s services, reach out to your local office.
