WildEarth Guardians v. United States Environmental Protection Agency, 770 F.3d 919

Clean Air Act program in the Colorado Plateau region adopted a regional cap-and-trade for sulfur dioxide by NM, Utah, and Wyoming, plus City of Albuquerque and Bernalillo County.
EPA approval required; states could use BART or an alternative better-than-BART program under Regional Haze Rule; 309 program chosen as better than BART.
D.C. Circuit previously invalidated aspects of the EPA’s methodology, prompting 2006 Rule revisions to allow a qualitative “clear weight of the evidence” analysis as an alternative to source-by-source BART.
Three participating states and local entities submitted 309 plans; several others declined to participate (notably NV, CA, AZ); EPA approved plans in 2012 after seeking public review.
Environmental groups challenged EPA’s approval on multiple grounds, arguing the 309 program did not yield greater reasonable progress than BART, and that nonparticipating states’ emissions and other data should undermine the finding; the court upheld EPA’s decision as not arbitrary or capricious.
New Mexico challenged inclusion of Escalante coal plant emissions in reasonable-progress analysis; the court rejected this challenge as not required by statute or rule and found EPA’s approval not arbitrary or capricious.

Issue	Plaintiff's Argument	Defendant's Argument	Held
Whether EPA’s better-than-BART determination was arbitrary or capricious	Environmental groups contended 309 did not outperform BART using rigorous, source-specific analysis.	EPA properly used Appendix Y presumptives and a weight-of-evidence approach allowed under regs.	No; EPA’s better-than-BART finding was not arbitrary or capricious.
Whether Appendix Y presumptive BART benchmark was properly used	Groups argued relying on Appendix Y misstates BART and undercuts state analyses.	Appendix Y presumptive rate is a reasonable simplifying assumption for a 309 program.	Proper; use of Appendix Y was permissible and timely challenged only within appropriate § 7607(b) window.
Whether qualitative factors can justify better-than-BART comparison	EPA should have used only quantitative § 51.308(e)(3) methods	Regulations permit qualitative weight-of-evidence as an alternative.	Yes; qualitative factors admissible under regulatory framework.
Whether there was a required minimum ‘critical mass’ of participating states	Insufficient number of participating states undermines regional program.	No statutory/regulatory minimum; EPA deferred to Western Regional Air Partnership.	No mandatory critical-mass requirement; EPA reasoned program could still be effective.

Oklahoma v. EPA, 723 F.3d 1201 (10th Cir. 2013) (states’ authority under Clean Air Act reviewed under APA standards)
Util. Air Regulatory Grp. v. EPA, 471 F.3d 1333 (D.C. Cir. 2006) (regulatory flexibility in setting rules under Regional Haze)
Am. Corn Growers Ass’n v. EPA, 291 F.3d 1 (D.C. Cir. 2002) (invalidated aggregation method for some BART analyses)
Center for Energy & Econ. Dev. v. EPA, 398 F.3d 653 (D.C. Cir. 2005) (approval of an alternative program upheld but via different methodology)
Nat’l Ass’n of Clean Air Agencies v. EPA, 489 F.3d 1221 (D.C. Cir. 2007) (deference to agency’s regulatory interpretation; weight-of-evidence)
Fed. Express Corp. v. Holowecki, 552 U.S. 389 (2008) (agency interpretations receive deference; regulatory language flexible)
Utah v. EPA, 750 F.3d 1182 (10th Cir. 2014) (timeliness and review of EPA rulemakings; exhaustion rules)
Alaska Dept. of Envtl. Conservation v. EPA, 540 U.S. 461 (2004) (deference to agency expertise in complex regulatory schemes)
Bowman Transp., Inc. v. Ark.-Best Freight Sys., Inc., 419 U.S. 281 (1974) (arbiter’s permissible inference from incomplete record; path reasonably discernible)