## Facts

- The EPA approved Missouri’s State Implementation Plan (SIP), which imposed sulfur dioxide (SO₂) and opacity limits on Union Electric’s coal-fired plants.
- Union Electric did not seek judicial review of EPA’s SIP approval within the Clean Air Act’s statutory review period.
- After approval, Union Electric obtained one-year state and local variances easing the SIP limits and sought extensions as variances expired.
- EPA notified Union Electric that its emissions violated the SIP’s SO₂ limits and that enforcement proceedings were probable.
- Union Electric pursued state administrative and judicial avenues for variances or SIP revisions, asserting the SIP limits were economically and technologically infeasible and unnecessary to achieve ambient air standards.
- Union Electric sued in federal district court to prevent EPA from initiating a federal enforcement action while state variance/revision proceedings were pending.

## Issues

1. Whether a federal district court may enjoin EPA from initiating a Clean Air Act enforcement action because a regulated entity is actively pursuing a state variance or SIP revision.
2. Whether equitable or due-process concerns permit federal courts to delay EPA’s pre-enforcement compliance and enforcement procedures.

## Decision

- The court of appeals reversed the district court’s injunction and directed dismissal of Union Electric’s complaint.
- Federal courts may not interfere with the Clean Air Act’s enforcement structure by enjoining EPA pre-enforcement actions based on pending state variance or revision proceedings.
- Union Electric was not denied a forum for its objections because feasibility and related contentions could be raised in state proceedings or as defenses in a federal enforcement case.
- The availability of injunctive enforcement (rather than penalties) weakened claims that immediate EPA action necessarily imposed unfair or unconstitutional consequences.

## Legal Principles

- The Clean Air Act provides exclusive, time-limited mechanisms for judicial review of SIP approvals; courts may not create additional pre-enforcement review through equitable injunctions.
- Pending state variance or SIP revision efforts do not bar EPA from initiating federal enforcement for violations of an approved SIP.
- Regulated entities may raise claims such as economic or technological infeasibility in state forums addressing variances/revisions and, where applicable, as defenses in federal enforcement litigation.

## Conclusion

The Eighth Circuit held that a district court lacked authority to halt EPA enforcement under an approved SIP merely because the regulated utility was pursuing state-level variances or plan revisions; the injunction was reversed and the suit dismissed to preserve the Clean Air Act’s prescribed enforcement and review scheme.


Union Elec. Co. v. EPA, 593 F.2d 299 (8th Cir. 1979)