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On September 5, 2025, the U.S. Court of Appeals for the Seventh Circuit issued an order staying the EPA’s December 17, 2024, final rule that determined parts of southeast Wisconsin failed to attain the 2015 ozone national ambient air quality standards (NAAQS), and consequently would be reclassified from “moderate” to the more restrictive “serious” nonattainment category. That reclassification was effective January 16, 2025, impacting portions of southeastern Wisconsin—specifically, Milwaukee and Ozaukee counties and parts of Waukesha, Washington, Racine, Kenosha, and Sheboygan counties.

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The reclassification imposed much more stringent requirements on sources in southeast Wisconsin emitting NOx and VOCs (precursors for ozone). Redesignation to serious nonattainment for ozone meant stationary sources were subject to reduced air permitting thresholds, more stringent emissions controls and offset requirements for new major sources and major modifications to major sources, alternative site analysis requirements, and more. For instance, the bump-up to “serious” nonattainment automatically reduced NOx and VOC stationary major source thresholds from 100 tons per year to 50 tons per year.

In February, the State of Wisconsin filed a petition for review of this reclassification in the U.S. Court of Appeals for the Seventh Circuit. Wisconsin subsequently moved for a stay of the reclassification on August 15. Wisconsin argued a stay was appropriate, in part, based on EPA’s failure to provide notice and opportunity for comment on the reclassification and consider out-of-state ozone transport, which significantly contributes to this region’s ozone nonattainment status.

That stay has now been granted by the Seventh Circuit. As a result, the EPA’s December 17, 2024, rule reclassifying parts of southeast Wisconsin is not in effect, and Wisconsin remains designated “moderate” nonattainment for the 2015 ozone NAAQS pending the Court’s review.

We will continue to monitor developments in this case. If you have questions about how this proposed rule may affect your business, please contact your Michael Best attorney or a member of our team listed on this alert.

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Seventh Circuit Stays Southeast Wisconsin “Serious” Nonattainment Bump-up

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