California Code, Revenue and Taxation Code - RTC § 2263

(1) The maximum property tax rate authorized by the enabling statute under which the district is organized; provided that any rate in excess of such maximum rate which is authorized by Section 35 of Chapter 1 of the Statutes of 1968 (First Extraordinary Session) and which was levied during either the 1971-1972 or the 1972-1973 fiscal year may continue to be levied.

(2) If no such maximum property tax rate is provided by statute, or if a maximum property tax rate is provided but such rate is applicable only to a portion of the purposes for which such district is levying an ad valorem property tax, the maximum rate shall be the rate levied by, or on behalf of, the district for either the 1971-1972 or the 1972-1973 fiscal year, at the option of the governing body of the district. If a district operates on a calendar year, the maximum rate which may be levied pursuant to this subdivision shall be that levied in either calendar 1972  1 or calendar 1973,  1 at the option of the governing body of the district.

(3) In addition, if the voters of a district, pursuant to provisions of the enabling statute under which the district is organized, have authorized an additional rate, such augmented rate shall be the maximum property tax rate.