California Code, Health and Safety Code - HSC § 44223

(a) In addition to any other fees specified in this code, the Vehicle Code, and the Revenue and Taxation Code, a district, except the Sacramento district, may levy a fee of up to two dollars ($2) on motor vehicles registered within the district. A district may impose the fee only if the district board adopts a resolution providing for both the fee and a corresponding program for the reduction of air pollution from motor vehicles pursuant to, and for related planning, monitoring, enforcement, and technical studies necessary for the implementation of, the California Clean Air Act of 1988 (Chapter 1568 of the Statutes of 1988), or for the attainment or maintenance of state or federal ambient air quality standards or the reduction of toxic air contaminant emissions from motor vehicles.

(b) In districts with nonelected officials on their boards, a resolution adopted pursuant to subdivision (a) shall be approved by both a majority of the board and a majority of the board members who are elected officials.

(c) A fee imposed pursuant to this section shall become effective on either April 1 or October 1, as provided in the resolution adopted by the board pursuant to subdivision (a).