Cal. VEH § 27156.2

Notwithstanding any other provision of law, any publicly owned authorized emergency vehicle operated by a peace officer, as defined in Section 830 of the Penal Code, any authorized emergency vehicle, as defined in Section 165 and used for fighting fires or responding to emergency fire calls pursuant to paragraph (2) of subdivision (b) or pursuant to subdivision (c) or (d) of that section, and any publicly owned authorized emergency vehicle used by an emergency medical technician-paramedic, as defined in Section 1797.84 of the Health and Safety Code, is exempt from requirements imposed pursuant to California law and the regulations adopted pursuant thereto for motor vehicle pollution control devices.