Cal. Water Code § 35005
No appointment of a proxy shall be valid, accepted, or vote allowed thereon at any district election unless it meets all of the following requirements:
(e) It shall be on a form as specified by the county elections official meeting the above requirements.
Every appointment of a proxy is revocable at the pleasure of the person executing it at any time before the person appointed as proxy shall have cast a ballot representing the votes for which the appointment was given.