EPA v. EME Homer City Generation, L. P.
The Supreme Court upheld the EPA's Cross-State Air Pollution Rule, which requires upwind states to cut smokestack pollution that drifts into downwind states, ruling that EPA could factor in the cost of reducing emissions rather than requiring cuts strictly proportional to each state's pollution contribution.
The decision also held that EPA could issue federal pollution-control plans immediately after rejecting a state's own plan, without first giving the state a further chance to submit a new one, reinforcing the EPA's authority to act decisively under the Clean Air Act's Good Neighbor Provision.
How it got here: The D.C. Circuit vacated EPA's Cross-State Air Pollution Rule entirely, and the EPA and environmental groups asked the Supreme Court to review that decision.
The Case in Depth
What happened
Air pollution from power plants and factories in upwind states drifts into downwind states, making it harder for those states to meet federal air-quality standards. EPA's Good Neighbor Provision requires upwind states to prevent their pollution from significantly harming air quality elsewhere. After the D.C. Circuit rejected an earlier EPA rule, the agency issued the Cross-State Air Pollution Rule, requiring 27 upwind states to cut nitrogen oxide and sulfur dioxide emissions, using a method that considered both pollution amounts and the cost of reducing them.
The question before the Court
Could the EPA make upwind states cut air pollution based on how cheaply they could reduce it, rather than strictly in proportion to how much pollution each state actually sent downwind?
Why it matters
Power plants and other industrial polluters in dozens of upwind states must reduce emissions under EPA's cost-based approach, meaning states that already invested in pollution controls won't be penalized for having done so. The ruling also confirms that the EPA can move quickly to impose federal pollution plans on states, without waiting to give them another chance to write their own rules first.
What changes now
The case is sent back to the D.C. Circuit for further proceedings consistent with the Court's ruling, meaning the Cross-State Air Pollution Rule remains in effect and upwind states must comply with EPA's cost-based emissions budgets. Individual states may still bring narrower, fact-specific challenges if they believe EPA required cuts beyond what's necessary for downwind attainment or below the one-percent significance threshold.
What this does not decide
The Court did not decide that EPA's cost-based approach is immune from all challenge: an upwind state can still bring a specific, as-applied challenge if it believes EPA forced it to cut emissions beyond what's needed for downwind attainment, or below the one-percent threshold EPA itself set for significance.
Concurrences and dissents
Dissent — Justice Scalia
Justice Scalia argued the majority let EPA rewrite the Clean Air Act by basing pollution cuts on cost-effectiveness rather than each state's actual share of pollution, calling this an undemocratic expansion of agency power unsupported by the statutory text. He also argued EPA abused its discretion by demanding states submit compliance plans before EPA announced what counted as a 'significant' contribution, undermining the Act's system of state-federal cooperation. He would have affirmed the D.C. Circuit's decision striking down the rule.
How the Court got there
The legal reasoning, step by step
- The Court first addressed whether EPA had to give states a fresh opportunity to submit a state plan after EPA calculated each state's pollution-reduction obligations. It read the Clean Air Act's plain text: once EPA rejects a state's plan as inadequate, the statute requires EPA to issue a federal plan within two years, with no exception for states still needing guidance on their good-neighbor obligations.
- The Court held that nothing in the statute conditions EPA's duty to issue a federal plan on first telling states exactly how much pollution they must cut, since Congress imposed that kind of information requirement explicitly elsewhere in the Act but not here.
- Turning to EPA's substantive interpretation of the Good Neighbor Provision, the Court applied Chevron deference — the principle that courts defer to a federal agency's reasonable reading of an ambiguous statute it administers — because the statute doesn't specify how to divide pollution-reduction responsibility among multiple contributing upwind states.
- The Court rejected the alternative approach requiring reductions strictly proportional to each state's pollution contribution, finding that method mathematically unworkable once a state contributes different ratios of pollution to different downwind states.
- The Court concluded that EPA's cost-based method — cutting the pollution that is cheapest to eliminate — was a permissible and even sensible way to fill the statutory gap, because it achieves the same downwind air-quality improvements at lower overall cost and avoids penalizing states that already installed pollution controls.
- The Court limited this holding by requiring that EPA not force any state to cut emissions beyond what's needed for downwind attainment or below the one-percent contribution threshold EPA itself set, though it found the record showed too few such instances to justify striking down the whole rule.
Doctrinal impact
Cases affected by this decision
Reaffirms Chevron U. S. A. Inc. v. Natural Resources Defense Council, Inc. (467 U. S. 837)
The Court relied on Chevron's framework to defer to EPA's reasonable interpretation of the ambiguous Good Neighbor Provision.