California Code, Elections Code - ELEC § 14240

(a) A person offering to vote may be orally challenged within the polling place only by a member of the precinct board upon any or all of the following grounds:

(b) A person, other than a member of a precinct board or other official responsible for the conduct of the election, shall not challenge or question any voter concerning the voter's qualifications to vote.

(c) If any member of a precinct board receives, by mail or otherwise, any document or list concerning the residence or other voting qualifications of any person or persons, with the express or implied suggestion, request, or demand that the person or persons be challenged, the board member shall first determine whether the document or list contains or is accompanied by evidence constituting probable cause to justify or substantiate a challenge. In any case, before making any use whatever of such a list or document, the member of the precinct board shall immediately contact the elections official, charged with the duty of conducting the election, and describe the contents of the document or list and the evidence, if any, received bearing on voting qualifications. The elections official shall advise the members of the precinct board as to the sufficiency of probable cause for instituting and substantiating the challenge and as to the law as herein provided, relating to hearings and procedures for challenges by members of the precinct board and determination thereof by a precinct board. The elections official may, if necessary, designate a deputy to receive and answer inquiries from precinct board members as herein provided.