In 2010, the EPA approved two permits for Shell to begin offshore exploratory drilling in the Arctic’s Chukchi and Beaufort Seas with the drillship Discoverer. REDOIL, a group representing the rights of the region’s indigenous peoples, contested the permits and argued that they violated the Clean Air Act by failing to require best available control technology (BACT) for emissions from the operation’s associated fleet of service vessels. In Resisting Environmental Destruction of Indigenous Lands (REDOIL) v. U.S. Environmental Protection Agency, the U.S. Court of Appeals for the Ninth Circuit found that the Act is ambiguous on the application of BACT to the drilling operation’s associated fleet and upheld the EPA’s interpretation that BACT is only required for the main drillship. The court was bound to defer to the agency’s reasonable interpretation under Chevron U.S.A., Inc. v. Natural Resources Defense Council, Inc. This Comment argues that the EPA could have ensured a more environmentally friendly outcome by embracing stricter applications of BACT that it has embraced in the past.