California Code, Revenue and Taxation Code - RTC § 6263

No person, other than the manufacturer who has received authorization to sell the motor vehicle in California or a person authorized by the manufacturer, shall install a vehicle emission control label on any motor vehicle.  No person shall remove, alter, deface, obscure, or destroy a vehicle emission control label or any label required to be affixed to any motor vehicle certified pursuant to the National Emissions Standards Act (42 U.S.C. Sec. 7521 et seq., and Subpart A (commencing with Sec. 86.078-3) of Part 86 of Title 40 of the Code of Federal Regulations).Any person who violates any provision of this section is guilty of a misdemeanor and is subject to a fine of not more than five thousand dollars ($5,000) or imprisonment in the county jail for not more than one year, or both that fine and imprisonment.