Concerning motor vehicle emission standards for Washington.

SB 5091 prevents Washington from adopting California's motor vehicle emission standards, requiring the state to instead set rules consistent with federal clean air standards. The bill directs the Department of Ecology to establish Washington-specific emission requirements that align with federal law but exclude California's standards, which the legislature states limits economic flexibility. It affects all motor vehicles registered in Washington, including new registrations and emissions testing requirements, while maintaining exemptions for electric vehicles, low-emission hybrids, and certain older or specialty vehicles. The law repeals prior requirements to adopt California standards and mandates the Department of Ecology to develop rules for vehicle emissions without referencing California's framework.