Cal. Health & Safety Code § 40717.5

(a) Any district that proposes to adopt or amend a rule or regulation pursuant to Section 40716 or 40717, which imposes any requirement on an indirect source to reduce vehicle trips or vehicle miles traveled, including, but not limited to, any rule or regulation affecting ridesharing or alternative transportation mode strategies, shall, prior to the adoption or amendment of the rule or regulation, do all of the following:
1. (1) Ensure, to the extent feasible, and based upon the best available information, assumptions, and methodologies that are reviewed and adopted at a public hearing, that the proposed rule or regulation would require an indirect source to reduce vehicular emissions only to the extent that the district determines that the source contributes to air pollution by generating vehicle trips that would not otherwise occur. In complying with this paragraph, a district shall make reasonable and feasible efforts to assign responsibility for existing and new vehicle trips in a manner that equitably distributes responsibility among indirect sources.
2. (2) Ensure that, to the extent feasible, the proposed rule or regulation does not require an indirect source to reduce vehicular trips that are required to be reduced by other rules or regulations adopted for the same purpose.
3. (3) Take into account the feasibility of implementing the proposed rule or regulation.
4. (4) Pursuant to Section 40922, consider the cost effectiveness of the proposed rule or regulation.
5. (5) Determine that the proposed rule or regulation would not place any requirement on public agencies or on indirect sources that would duplicate any requirement placed upon those public agencies or indirect sources as a result of another rule or regulation adopted pursuant to Section 40716 or 40717.
(b) A district may delegate to any city or county the responsibility to implement a rule or regulation that is subject to subdivision (a). However, if an indirect source subject to the rule or regulation has sites located both within and outside of the jurisdiction of a city or county to which that responsibility has been delegated, the indirect source may elect to be subject to the implementation of that rule or regulation only by the district. Notwithstanding Section 40454, an indirect source that elects to be regulated only by a district pursuant to this subdivision may also elect to include sites under district regulation that would not otherwise be subject to district regulation, and, in that event, shall not be subject to the implementation by a city or county of any requirement contained in that rule or regulation.
(c)
1. (1) Nothing in this section constitutes an infringement on the existing authority of counties and cities to plan, control, or condition land use, or on the ability of a city, county, or other public agency to impose trip reduction measures pursuant to a voter-mandated growth management program.
2. (2) Nothing in this section provides or transfers new authority over land use to a district.