Congress enacted the Clean Air Act (CAA) to achieve and maintain national ambient air quality standards (NAAQS). The 1977 Amendments required states with areas not meeting the NAAQS (nonattainment areas) to adopt a preconstruction permit program for any new or modified "major stationary source." The nonattainment provisions did not define "stationary source." In the late 1970s, the Environmental Protection Agency (EPA) initially took a restrictive view that treated each individual emissions unit within a plant as a separate "source" for nonattainment permitting, making many intra-plant equipment changes subject to permitting. In 1981, the EPA, under a new administration, adopted a more flexible "bubble concept," defining "stationary source" on a plantwide basis so that a plant could modify or replace individual units without obtaining a permit so long as total plant emissions did not increase. The Natural Resources Defense Council (NRDC) challenged the rule in the D.C. Circuit, arguing the statute compelled a unit-by-unit approach. The D.C. Circuit set aside the EPA's regulation, concluding that the CAA did not allow the plantwide definition in nonattainment areas. The Supreme Court granted certiorari.
Does the Clean Air Act permit the EPA to define the term "stationary source" to include an entire plant (the "bubble concept") for purposes of the nonattainment new-source review program, and more broadly, what standard governs a court's review of an agency's interpretation of an ambiguous statute it administers?
Chevron established a two-step framework for reviewing an agency's interpretation of a statute it administers: (1) Step One: Using the traditional tools of statutory interpretation, a court asks whether Congress has spoken to the precise question at issue. If the statute is unambiguous, the court must give effect to Congress's clear intent. (2) Step Two: If the statute is silent or ambiguous with respect to the specific issue, the question for the court is whether the agency's interpretation is a permissible (reasonable) construction of the statute; if so, the court defers to the agency's view, even if the court might have preferred a different reading. The doctrine rests on the premise that statutory ambiguity is an implicit delegation from Congress to the agency to make reasonable policy choices within statutory bounds, subject to the APA's arbitrary-and-capricious review. (Note: Chevron was overruled in 2024; historically, courts applied these steps when an interpretation was issued with the force of law.)
Yes. The Clean Air Act's use of "stationary source" in the nonattainment provisions is ambiguous, and the EPA's plantwide (bubble) definition is a permissible construction. The Supreme Court reversed the D.C. Circuit and upheld the EPA's regulation.
The Court, per Justice Stevens, began by emphasizing that when Congress leaves ambiguity in a statute it has charged an agency to administer, it implicitly delegates authority to the agency to fill the gap reasonably. Applying Step One, the Court concluded the CAA did not unambiguously resolve whether "stationary source" refers to each individual emissions unit or to an entire plant. The definitional language elsewhere in the Act (e.g., § 111's reference to "any building, structure, facility, or installation") could accommodate a plantwide reading, and the statutory structure revealed competing goals: preventing air quality deterioration while promoting economic growth and modernization. Legislative history was inconclusive. Proceeding to Step Two, the Court found the EPA's bubble concept to be a permissible (reasonable) policy choice that harmonized the Act's dual aims. Treating an entire plant as a single source allowed plants to retool and improve efficiency without triggering permits so long as total emissions did not increase, thereby encouraging technology upgrades while still controlling aggregate emissions. The Court underscored institutional competence and political accountability: agencies, not courts, are better suited to balance complex technical and policy considerations, and agency policy can legitimately change with administrations so long as the new interpretation is reasonable and explained. Finally, the Court noted that judicial review under the APA remains a backstop; courts ensure the agency acted within statutory limits and did not act arbitrarily or capriciously, but they do not substitute their own policy preferences for the agency's.
Chevron became the central framework for judicial deference to agency statutory interpretations, shaping the modern administrative state. It channeled judicial review into a structured inquiry (text first; deference if ambiguity remains) and rationalized the role of expertise and political accountability in regulatory policy. The decision influenced how agencies write rules, how courts decide challenges, and how lawyers brief statutory cases. Over time, the Court limited and refined Chevron through doctrines like Step Zero (United States v. Mead: Chevron applies only when Congress delegated authority to make rules with the force of law and the agency interpretation was rendered in exercise of that authority), Brand X (allowing agencies to adopt reasonable interpretations that could supersede prior judicial readings of ambiguous statutes), and the "major questions" doctrine (courts require clear congressional authorization for agency assertions of vast economic and political significance). In 2024, Loper Bright Enterprises v. Raimondo overruled Chevron, instructing courts to exercise independent judgment on statutory meaning while recognizing that agency views may still receive Skidmore respect based on their power to persuade. Nonetheless, Chevron remains essential for understanding decades of administrative law, statutory interpretation, and the ongoing debate over the proper roles of courts and agencies.
Chevron v. NRDC provided a durable, administrable framework that balanced fidelity to congressional text with deference to agency expertise in the face of statutory ambiguity. By instructing courts to apply Congress's clear directives and otherwise to accept reasonable agency choices, Chevron aimed to align adjudication with democratic accountability and technical competence. Its two-step inquiry became the lingua franca of administrative law for four decades.