Cal. Veh. Code § 27150.5
Any person holding a retail seller's permit who sells or installs an exhaust system, or part thereof, including, but not limited to, a muffler, in violation of Section 27150.1 or 27150.2 or the regulations adopted pursuant thereto, shall thereafter be required to install an exhaust system, or part thereof, including, but not limited to, a muffler, which is in compliance with such regulations upon demand of the purchaser or registered owner of the vehicle concerned, or to reimburse the purchaser or registered owner for the expense of replacement and installation of an exhaust system, or part thereof, including, but not limited to, a muffler, which is in compliance, at the election of such purchaser or registered owner.
Ca. Veh. Code § 27150.5