I. Introduction
Climate change is one of the most pressing issues facing the United States, raising questions about the extent of the federal government's legal authority in regulating greenhouse gas emissions. The Environmental Protection Agency (EPA) plays a crucial role in addressing climate change by monitoring air pollution and enforcing federal environmental laws. However, the EPA did not create the Clean Air Act. Congress passed the law in 1970, and President Richard Nixon signed it into law, establishing the legal framework under which the EPA regulates air pollution.1 The agency’s authority to address climate change therefore depends on the powers Congress has granted it, the Supreme Court’s interpretation of federal law, and the decisions of presidential administrations. Although the EPA has significant authority to regulate greenhouse gas emissions, its ability to enforce climate policies remains subject to legal limitations. Understanding these limitations is essential to evaluating how effectively the federal government can respond to climate change. II. The EPA’s Legal Authority to Regulate Greenhouse Gas Emissions The EPA’s legal capacity to regulate greenhouse gas emissions is primarily based on the Clean Air Act, which establishes a framework for controlling air pollution that threatens public health and welfare.2 Different provisions of the law authorize the EPA to oversee emissions from different sources. For example, Section 202(a)(1) addresses emissions from new motor vehicles and requires the EPA Administrator to establish emission standards when the statutory endangerment criteria are met.3 Section 111 provides a separate framework for regulating emissions from certain stationary sources, including power plants.4 The Clean Air Act also defines “air pollutant” broadly enough to include greenhouse gases.5 A major development in federal climate regulation occurred in 2007, when the Supreme Court issued its decision in Massachusetts v. EPA.6 The Court held that greenhouse gases fall within the Clean Air Act’s definition of air pollutants. It rejected the EPA’s argument that the agency could decline to regulate greenhouse gas emissions from new motor vehicles for reasons not supported by the statute. Instead, the EPA had to determine whether these emissions contributed to air pollution that could reasonably be anticipated to endanger public health or welfare. If the EPA made an affirmative endangerment finding, Section 202(a)(1) required it to regulate the relevant emissions.7 This ruling established an important legal foundation for federal climate policy because it confirmed that the Clean Air Act could apply to greenhouse gases, even though Congress enacted the law decades before climate change became a central issue in national policy debates. However, Massachusetts v. EPA did not grant the EPA unlimited authority to address climate change. The case specifically concerned emissions from new motor vehicles under Section 202(a)(1). The agency must still act within the powers delegated by Congress and comply with the requirements of the relevant statutory provisions. Consequently, the Clean Air Act provides both the legal foundation for regulating greenhouse gas emissions and the boundaries within which the EPA must operate.
III. Limitations on the EPA’s Authority Although the Supreme Court has recognized the EPA’s authority to regulate greenhouse gases, other decisions have established limits on how that authority can be exercised. One of the most significant examples is West Virginia v. EPA, which addressed the EPA’s authority to regulate carbon dioxide emissions from existing power plants under Section 111(d) of the Clean Air Act.8 The Court concluded that Section 111(d) did not clearly authorize the EPA to implement the Clean Power Plan’s approach of shifting electricity generation away from higher-emitting power plants toward lower-emitting sources. The decision relied on the major questions doctrine, which requires clear congressional authorization when an agency claims significant regulatory power over an issue of major economic and political importance.9 The Court determined that the EPA’s generation-shifting approach exceeded the authority Congress had granted under the statutory provision at issue. This ruling did not eliminate the EPA’s authority to regulate greenhouse gas emissions from power plants. Instead, it restricted the agency’s ability to use Section 111(d) to implement this particular approach without clear congressional authorization. The case demonstrates that federal agencies cannot rely solely on broad interpretations of existing laws when pursuing major policy changes. Their actions must be supported by the authority Congress has granted. As a result, Supreme Court rulings shape federal climate change regulation by determining which policies are legally permissible. Another important development occurred in Loper Bright Enterprises v. Raimondo, in which the Supreme Court overturned the Chevron deference framework.10 Under the former framework, courts generally deferred to reasonable agency interpretations of ambiguous statutes in certain circumstances. After Loper Bright, courts must exercise independent judgment when interpreting federal statutes and determining whether an agency has acted within its statutory authority. Courts may still consider an agency’s expertise and reasoning, but they cannot defer to an agency’s interpretation simply because a statute is ambiguous.
This decision has important implications for the EPA because the agency’s interpretations of the Clean Air Act must withstand independent judicial review. However, Loper Bright did not eliminate the EPA’s scientific and technical expertise, automatically invalidate existing regulations, or prevent Congress from expressly delegating discretionary authority to federal agencies. Instead, it changed the legal framework courts use to evaluate agency interpretations of federal law. Together, West Virginia v. EPA and Loper Bright demonstrate that the EPA’s authority depends not only on congressional legislation but also on how courts interpret the scope of that authority.
IV. Presidential Administrations and Changes in Climate Policy
Presidential administrations also influence how the EPA regulates greenhouse gas emissions. The Obama administration pursued a stronger federal climate policy, including the Clean Power Plan, which sought to reduce carbon dioxide emissions from existing power plants. However, the Plan faced legal challenges and never fully went into effect. The first Trump administration repealed the Clean Power Plan in 2019 and replaced it with the Affordable Clean Energy rule, which adopted a different approach to regulating emissions from coal-fired power plants.11 In 2021, the U.S. Court of Appeals for the District of Columbia Circuit vacated the EPA’s repeal and replacement rule.12 The Supreme Court subsequently reversed that judgment in West Virginia v. EPA, demonstrating how disputes over federal climate policy can move through multiple levels of judicial review. The second Trump administration began in 2025 and brought renewed efforts to revise or reverse federal climate policies. However, presidential administrations cannot automatically eliminate existing regulations simply because their policy priorities change. The Administrative Procedure Act (APA) establishes important requirements for federal agencies when they adopt, revise, or repeal regulations. Under 5 U.S.C. § 706(2)(A), courts may set aside agency actions that are arbitrary, capricious, an abuse of discretion, or otherwise not in accordance with law. Section 706(2)(C) also allows courts to set aside agency actions that exceed their statutory authority.13
In FCC v. Fox Television Stations, Inc., the Supreme Court explained that an agency changing its policy generally must acknowledge the change and provide a reasoned explanation for its decision.14 An agency does not necessarily have to prove that its new policy is better than its previous one simply because it has changed course. However, it may need to address important facts, prior findings, and reliance interests associated with its earlier position. Reducing an agency’s budget also does not automatically repeal the Clean Air Act or eliminate the agency’s existing legal obligations. Although presidential administrations can influence the direction and enforcement of federal climate policy, their actions remain subject to applicable statutory requirements, administrative procedures, and judicial review. These legal safeguards limit the extent to which environmental regulations can be changed without a sufficient legal basis.
V. Congressional Authority and the Separation of Powers
The legal limits on federal climate regulation reflect the constitutional separation of powers among Congress, the executive branch, and the judiciary. Congress has the authority to enact environmental legislation and determine the powers delegated to agencies such as the EPA. The executive branch is responsible for implementing those laws, while the EPA develops and enforces regulations within its statutory authority. The judiciary interprets federal law and reviews agency decisions when legal disputes arise. These separate responsibilities help prevent any single branch of government from exercising unlimited authority over environmental policy.
For example, Massachusetts v. EPA established that greenhouse gases could be regulated under the Clean Air Act, while West Virginia v. EPA demonstrated that the agency’s authority remains constrained by statutory language and judicial interpretations of federal law. In Loper Bright Enterprises v. Raimondo, the Court further emphasized the judiciary’s responsibility to independently interpret federal statutes. These cases illustrate the relationship between congressional intent and executive implementation. When Congress grants clear authority for a particular regulatory approach, the EPA has a stronger legal foundation for pursuing it. Conversely, when the agency attempts to implement policies that exceed its delegated powers, courts may invalidate those actions. The major questions doctrine reinforces this limitation in certain cases involving issues of exceptional economic and political significance, while Loper Bright requires courts to exercise independent judgment when interpreting statutory provisions.
Congress therefore plays a crucial role in determining the future of federal climate policy. If lawmakers want to authorize major regulatory approaches that are not clearly supported by existing statutory language, they can enact legislation expressly granting the EPA those powers. Clear congressional authorization could provide a more secure legal foundation for ambitious climate policies and reduce uncertainty about the scope of the agency’s authority. Ultimately, the balance between congressional legislation, executive implementation, and judicial review will continue to shape how the federal government addresses greenhouse gas emissions.
VI. Conclusion
The federal government has significant authority to regulate greenhouse gas emissions through the EPA, particularly under the Clean Air Act, but that authority is subject to important legal limits. Supreme Court decisions such as Massachusetts v. EPA and West Virginia v. EPA demonstrate that the EPA can regulate greenhouse gases while remaining constrained by congressional legislation and judicial interpretations of federal law. Meanwhile, Loper Bright Enterprises v. Raimondo requires courts to independently interpret federal statutes rather than automatically defer to agency interpretations of ambiguous language.
The Administrative Procedure Act and FCC v. Fox Television Stations also establish that presidential administrations may change environmental policies but must provide legally adequate explanations and comply with applicable procedures. These requirements do not prevent administrations from changing their regulatory priorities, but they help ensure that agency decisions remain within the law. Ultimately, the federal government’s ability to address climate change depends on both the legal authority Congress grants and the way that authority is exercised by the executive branch. Understanding these limits is essential to evaluating the future of federal climate regulation and determining how effectively the United States can respond to climate change within the boundaries of the law.
Footnotes 1 Clean Air Act, 42 U.S.C. §§ 7401–7671q (2023); U.S. Env’t Prot. Agency, Evolution of the Clean Air Act, https://www.epa.gov/clean-air-act-overview/evolution-clean-air-act (last visited Oct. 23, 2026). 2 42 U.S.C. § 7401 et seq. 3 Clean Air Act § 202(a)(1), 42 U.S.C. § 7521(a)(1) (2023). 4 Clean Air Act § 111, 42 U.S.C. § 7411 (2023). 5 Clean Air Act § 302(g), 42 U.S.C. § 7602(g) (2023). 6 Massachusetts v. EPA, 549 U.S. 497, 528–32 (2007). 7 Id. at 532–35; 42 U.S.C. § 7521(a)(1). 8 West Virginia v. EPA, 597 U.S. 697, 723–35 (2022). 9 Id. at 721–24, 732–35. 10 Loper Bright Enters. v. Raimondo, 603 U.S. 369, 400–13 (2024). 11 U.S. Env’t Prot. Agency, Affordable Clean Energy Rule, https://www.epa.gov/stationary-sources-air-pollution/affordable-clean-energy-rule (last visited Oct. 23, 2026). 12 Am. Lung Ass’n v. EPA, 985 F.3d 914, 995–1003 (D.C. Cir. 2021), rev’d sub nom. West Virginia v. EPA, 597 U.S. 697 (2022). 13 Administrative Procedure Act, 5 U.S.C. § 706(2)(A), (C) (2024). 14 FCC v. Fox Television Stations, Inc., 556 U.S. 502, 514–16 (2009).