California Code, Vehicle Code - VEH § 27501

(a) No dealer or person holding a retail seller's permit shall sell, offer for sale, expose for sale, or install on a vehicle for use on a highway, a pneumatic tire which is not in compliance with regulations adopted pursuant to Section 27500.  This subdivision shall not apply to any person who installs on a vehicle, as part of an emergency service rendered to a vehicle upon a highway, a spare tire with which such disabled vehicle was equipped.

(b) No person shall use on a highway a pneumatic tire which is not in conformance with such regulations.