California Code, Government Code - GOV § 65863.3

(a) A public agency shall not increase the minimum parking requirement that applies to a single-family residence as a condition of approval of a project to remodel, renovate, or add to a single-family residence provided that the project does not cause the single-family residence to exceed any maximum size limit imposed by the applicable zoning regulations, including, but not limited to, height, lot coverage, and floor-to-area ratio.

(b) For purposes of this section, “public agency” means the state or any state agency, board or commission, any city, county, city and county, including charter cities, or special district, or any agency, board, or commission of the city, county, city and county, special district, joint powers authority, or other political subdivision.

(c) The Legislature finds and declares that the imposition of mandatory parking minimums can increase the cost of housing, limit the number of available units, lead to an oversupply of parking spaces, and increased greenhouse gas emissions.  Therefore, this section shall be interpreted in favor of the prohibition of the imposition of mandatory parking minimums as outlined in this section.

(d) This section shall not be construed to allow a local agency to impose parking restrictions that are more restrictive than the requirements a local agency is authorized to impose under Article 2 (commencing with Section 66314) of Chapter 13 if the single-family residence is on the same lot as an accessory dwelling unit.