Cal. Elec. Code § 3112
Whenever by any statute of the United States, provision is made for vote by mail, an application for a vote by mail ballot made under that law may be given the same effect as an application for a vote by mail ballot made under this code.
If, by any federal statute, provision is made for the transmission of applications for vote by mail status to the Secretary of State, he or she shall transmit the applications to the county elections official of the county in which the applicant claims residence, or for a military or overseas voter qualified pursuant to paragraph (2) of subdivision (b) of Section 321, to the county in which the applicant's parent or legal guardian resided when the parent or legal guardian last lived within the territorial limits of the United States or the District of Columbia.
Ca. Elec. Code § 3112