By Jennifer Cassel

On March 5, 2010, Wyoming’s Supreme Court affirmed the issuance of a Clean Air Act (“CAA”) permit for a coal-fired power plant, holding that the plant is not required to limit Greenhouse Gas (“GHG”) emissions because GHGs are not subject to Best Available Control Technology requirements under the CAA. Powder River Basin Res. Council v. Wyoming Dep’t of Envtl. Quality, 226 P.3d 809 (Wyo. 2010) (“PRBRC”). In PRBRC, plaintiffs PRBRC and Sierra Club challenged the air permit issued to Basin Electric Power Cooperative (“Basin Electric”) for the Dry Fork Station power plant, arguing that the permit was improperly issued because it failed to require Basin Electric to limit GHG emissions. The plaintiffs argued that GHGs, including CO2, are “subject to regulation” under the CAA and thus permit limits must be established for the plant’s GHG emissions. The Wyoming Supreme Court rejected plaintiffs’ argument, noting that, while the EPA had agreed to reconsider whether CO2 is ‘subject to regulation’ under the CAA, in agreeing to do so EPA did not stay its interpretation that CO2 is not currently subject to regulation under the CAA. Moreover, the Court reasoned, even if EPA were to determine that CO2 is subject to regulation under the CAA, the plaintiffs did not establish that GHGs were subject to regulation when the permit was issued.