Whitman v. American Trucking Assns., Inc.
The Supreme Court upheld the Environmental Protection Agency's authority to set national air-quality standards under the Clean Air Act, ruling that the law's instruction to protect public health with an adequate margin of safety gave the agency enough guidance to satisfy the Constitution's limits on delegating lawmaking power.
At the same time, the Court held the EPA could not consider the cost of compliance when deciding how strict those standards should be, and sent back a separate dispute over how the new ozone standard should be phased in for areas that fail to meet it.
How it got here: The D.C. Circuit found the EPA's interpretation of the statute unconstitutional and questioned its ozone implementation approach; both sides asked the Supreme Court to review different parts of that ruling.
The Case in Depth
What happened
In 1997 the EPA tightened national air-quality standards for ozone (smog) and fine particulate matter (soot). Trucking companies, other businesses, and several states sued, arguing the EPA had been handed unchecked power to regulate the economy and that it should have weighed the economic costs of compliance, while also disputing how the new ozone rules would be phased in for polluted areas.
The question before the Court
Could Congress let the EPA set nationwide air-quality standards using only the phrase "requisite to protect public health," and could the agency factor in the cost of compliance when setting those standards?
Why it matters
The ruling let the EPA keep enforcing tighter smog and soot standards nationwide without rewriting the Clean Air Act, affecting industries, cities, and millions of residents in areas with unhealthy air. It also means regulators must set health standards based purely on health science, not on how expensive compliance will be for factories, utilities, and other polluters.
What changes now
The case returns to the D.C. Circuit and then to the EPA, which must develop a new, reasonable interpretation of how existing ozone-implementation rules apply to the revised standard, since the Court rejected the agency's prior approach. The core air-quality standards themselves remain in effect, cost considerations remain off-limits in setting them, and any remaining challenges to the standards go back to the lower court for further proceedings.
What this does not decide
The Court did not decide whether the EPA's revised ozone and particulate standards were scientifically sound, nor did it resolve every implementation detail for phasing in the new ozone standard — it only rejected the EPA's specific legal theory and left the agency to craft a new approach. It also did not adopt Justice Thomas's suggestion that the delegation test itself might be too permissive.
Concurrences and dissents
Concurrence — Justice Thomas
Justice Thomas agreed the statute passed the Court's existing 'intelligible principle' test but wrote separately to flag a deeper concern: the Constitution's text says all legislative power is vested in Congress, not that delegations are fine so long as some guiding principle exists. He suggested that in some cases a decision could be significant enough to count as 'legislative' even if the principle guiding it is intelligible, and invited a future case to reconsider the doctrine.
Concurrence in part — Justice Stevens
Justice Stevens, joined by Justice Souter, agreed the delegation was constitutional but objected to the majority's framing that the power given to the EPA is not really 'legislative power.' He argued it is more honest and consistent with ordinary English and the Constitution's text to call agency rulemaking legislative power that Congress may permissibly delegate so long as it provides an intelligible principle.
Concurrence in part — Justice Breyer
Justice Breyer agreed the EPA cannot consider costs in setting the standards, but would have relied on legislative history showing Congress wanted the Clean Air Act to be 'technology forcing' rather than on a strict textual presumption. He also emphasized that the statute still gives the EPA considerable discretion to consider comparative health risks and context, so it does not require eliminating all risk regardless of cost.
How the Court got there
The legal reasoning, step by step
- The Court first asked what the statute's cost-related language actually says, since determining what a law authorizes comes before deciding whether that authorization is constitutional. It found the text instructing EPA to protect 'public health' with 'an adequate margin of safety' contains no mention of cost, and other Clean Air Act provisions expressly mention cost elsewhere, showing Congress knew how to authorize cost consideration when it wanted to.
- Applying the principle that Congress does not hide major policy decisions in vague statutory corners, the Court concluded that if lawmakers meant to let the EPA weigh economic costs against health benefits in setting these standards, they would have said so clearly, given how central this provision is to the entire Clean Air Act.
- Turning to the constitutional challenge, the Court applied the 'intelligible principle' test — the longstanding rule that Congress may hand an agency decision-making authority only if it provides a guiding standard for how to use that power, so the agency isn't essentially legislating from scratch.
- The Court found the requirement that standards be 'requisite' — sufficient but not more than necessary — to protect public health was comparable to other broad grants of authority the Court had already approved, such as letting an agency act to avoid an 'imminent hazard to public safety.'
- The Court also rejected the idea that an agency can fix an unconstitutionally vague delegation by voluntarily narrowing its own interpretation, reasoning that deciding which portion of undefined power to use would itself be an exercise of the very lawmaking authority Congress cannot hand over.
- On the ozone phase-in dispute, the Court applied the two-step framework for reviewing an agency's reading of an ambiguous statute: if the law's meaning is clear, that controls, but if it is ambiguous, courts defer to a reasonable agency interpretation. The Court found the statute ambiguous about how two implementation subparts interact, but concluded the EPA's chosen interpretation went beyond reasonable ambiguity by effectively erasing one subpart's detailed limits on the agency's own discretion.
Doctrinal impact
Cases affected by this decision
Reaffirms Lead Industries Assn., Inc. v. EPA (647 F. 2d 1130)
The Court agreed with this lower-court ruling that EPA cannot weigh compliance costs in setting air-quality standards.
Reaffirms Chevron U. S. A. Inc. v. Natural Resources Defense Council, Inc. (467 U. S. 837)
The Court applied Chevron's two-step framework to review EPA's interpretation of the ozone implementation provisions.