California Code, Health and Safety Code - HSC § 12541.1

(a) A special district which provides fire protection, prevention, or suppression services may adopt an ordinance or regulation to prohibit or regulate the sale, use, or discharge of fireworks within that special district.

(b) If the county or city in which any area of the special district is located has adopted an ordinance or regulation to prohibit or regulate the sale, use, or discharge of fireworks within that county or city, the ordinance or regulation adopted by the county or city shall prevail over the ordinance or regulation adopted by the special district within any area of the special district which is within that county or city, and only the ordinance or regulation adopted by the county or city shall be operative in that area of the special district.

(c) If any area of a special district encompasses lands which are a state responsibility area, as defined in Sections 4125 and 4126 of the Public Resources Code, any regulation or prohibition of the state with respect to the sale, use, or discharge of fireworks within the state responsibility area shall prevail over any ordinance or regulation of the special district within that area.