Cal. ELEC § 2101

(a) A person entitled to register to vote shall be a United States citizen, a resident of California, not imprisoned for the conviction of a felony, and at least 18 years of age at the time of the next election. (b) A person entitled to preregister to vote in an election shall be a United States citizen, a resident of California, not imprisoned for the conviction of a felony, and at least 16 years of age. (c) For purposes of this section, the following definitions apply: (1) “Imprisoned” means currently serving a state or federal prison term. (2) “Conviction” does not include a juvenile adjudication made pursuant to Section 203 of the Welfare and Institutions Code.