Cal. Health & Safety Code § 17958.5

(a) Except as provided in subdivision (c) and in Section 17922.6, in adopting the ordinances or regulations pursuant to Section 17958, a city or county may make those changes or modifications in the requirements contained in the provisions published in the California Building Standards Code and the other regulations adopted pursuant to Section 17922, including, but not limited to, green building standards, as it determines, pursuant to the provisions of Section 17958.7, are reasonably necessary because of local climatic, geological, or topographical conditions.
(b) For purposes of this section, a city or county may make reasonably necessary modifications to the requirements, adopted pursuant to Section 17922, including, but not limited to, green building standards, contained in the provisions of the code and regulations on the basis of local conditions.
(c) Commencing October 1, 2025, to June 1, 2031, inclusive, a city or county shall not make a change or modification as described in subdivision (a) or (b), including to green building standards, that is applicable to residential units, unless one of the following conditions is met:
1. (1) The changes or modifications are substantially equivalent to changes or modifications that were previously filed by the governing body of the city or county and were in effect as of September 30, 2025.
2. (2) The commission deems those changes or modifications necessary as emergency standards to protect health and safety.
3. (3) The changes or modifications relate to home hardening.
4. (4) The building standards relate to home hardening and are proposed for adoption by a local fire prevention district pursuant to Section 13869.7.
5. (5) The changes or modifications are necessary to implement a local code amendment that is adopted to align with a general plan approved on or before June 10, 2025, and that permits mixed-fuel residential construction consistent with federal law while also incentivizing all-electric construction as part of an adopted greenhouse gas emissions reduction strategy.
6. (6) The changes or modifications are related to administrative practices, are proposed for adoption during the intervening period pursuant to Section 18942, and exclusively result in any of the following:
  1. (A) Reductions in time for a local agency to issue a postentitlement permit.
  2. (B) Alterations to a local agency’s postentitlement fee schedule.
  3. (C) Modernization of, or adoption of, new permitting platforms and software utilized by the local agency.
  4. (D) Reductions in cost of internal operation for a local agency.
  5. (E) Establishment, alteration, or removal of local programs related to enforcement of building code violations or complaints alleging building code violations.