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Montana Environmental Information Center v. Thomas

ELR Citation: 48 ELR 20156
Nos. 16-71933, (9th Cir., 08/30/2018)

The Ninth Circuit denied an environmental group's petition to review EPA's approval of a Montana SIP revision. The group argued that the approval was arbitrary and capricious because Montana's Department of Environmental Quality interpreted one of the SIP's provisions less stringently than the CAA allowed, and the department's interpretation carried the force of law. But the court disagreed, finding that the provision was ambiguous because the department and the Agency reasonably interpreted it to mean two different things, and concluding that it was appropriate to defer to the Agency's reasonable interpretation of the ambiguous text. The court therefore denied the group's petition for review.