Cal. Elections Code § 21605

(a) After redistricting or districting, a council shall not adopt new council district boundaries until after the next federal decennial census, except under the following circumstances: (1) A court orders the council to redistrict. (2) The council is settling a legal claim that its council district boundaries violate the United States Constitution, the federal Voting Rights Act of 1965 (52 U.S.C. Sec. 10301 et seq.), or this article. (3) The boundaries of the city change by the addition of territory pursuant to Section 21603 or by the subtraction of territory. (4) The number of council members elected by districts or from districts is increased or decreased. (5) An independent redistricting commission is established pursuant to Section 23003 to adopt new council districts between federal decennial censuses and the districts being replaced were adopted by the city council. (b) This section does not prohibit a council from adopting council districts between federal decennial censuses if the council is adopting council districts for the first time, including when a city adopts council districts for the purpose of transitioning from electing its council members in at-large elections to elections by districts or from districts.