Ninth Circuit rules Section 233 preempts state rules on airport ground emissions
Codoni v. Port of Seattle (No. 25-2830) resolves the scope of Clean Air Act Section 233 preemption for large airports, sharpening the boundary between state and local air-quality authority and federal air transport regulation.
On September 23, 2026, the U.S. Court of Appeals for the Ninth Circuit decided Codoni v. Port of Seattle, No. 25-2830, and Alaska Airlines prevailed on federal preemption. The case addresses how far Section 233 of the Clean Air Act — the federal regime governing emissions from aircraft and airport ground operations at "major" airports — displaces state and local regulation. The available source does not set out the panel's reasoning or precise disposition, so the boundaries of the holding should be confirmed against the opinion.
Why it matters: Section 233 is among the most consequential preemption provisions in US environmental law. State agencies and local air districts have long used indirect-source review, emissions inventories, and ground-level mobile-source rules to control diesel activity around airports. Subsection (a)(2) gives the Administrator exclusive authority over emission standards for jet and aircraft propulsion, while subsection (c)(5) preserves certain local building, zoning, and land-use decisions. A decision fixing that line reshapes compliance planning for ports, airport authorities, airlines, their ground-service contractors, and states litigating local climate authority.
What to watch: rehearing en banc and certiorari petitions; how non-aircraft ground-support vehicles are treated; and related litigation over rules that survive the Section 233(c) exceptions.