Section 21506 Of Chapter 6. Supervisorial Districts From California Elections Code >> Division 21. >> Chapter 6.

. The term of office of any supervisor who has been elected and whose term of office has not expired shall not be affected by any change in the boundaries of the district from which he or she was elected. At the first election for county supervisors in each county following adjustment of the boundaries of supervisorial districts, a supervisor shall be elected for each district under the readjusted district plan that has the same district number as a district whose incumbent's term is due to expire. A change in the boundaries of a supervisorial district shall not be made within 45 days before the first day for circulating nomination papers for an election of supervisors in the county or between the direct primary election and the general election.