Wyoming v. EPA consolidated two petitions for review of a portion of Wyoming’s plans to reduce visibility impacts from two powerplants, Wyodak and Naughton. First, the Tenth Circuit held EPA was incorrect to disapprove Wyoming’s best available retrofit technology determination for Wyodak because EPA based its disapproval on noncompliance with guidelines that are optional to determine the best available retrofit technology for Wyodak. These same guidelines are nonbinding on Naughton as well, and the court held the petitioners failed to persuade the court that EPA’s approval of Naughton was arbitrary and capricious because the petitioners did not establish why Wyoming’s best available retrofit technology determination was arbitrary and capricious. The Tenth Circuit’s decision will allow states to use nonbinding regulations to guide decision making without being punished for not adhering to them.



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