Several states have said in public comments to a U.S. EPA proposed rule that the EPA has exceeded its authority under the Clean Air Act. Under the proposed rule, 36 states would be required to modify their state implementation plans (“SIPs”) to require them to impose restrictions on facilities to control emissions from sources during times of start-up, shutdown, and equipment malfunction. The states argue that, while the EPA has the authority to set national ambient air quality standards, it left to the discretion of the states how to meet the standards. Under the Clean Air Act, the EPA may call for revisions to a state’s SIP if the EPA finds the plan to be substantially inadequate; however, the current proposed rule, would substitute EPA policy preference for those of the states under their SIPs.