CA Elec Code Section 2101

(a)

A person entitled to register to vote shall be a United States citizen, a resident of California, not imprisoned or on parole 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 or on parole for the conviction of a felony, and at least 16 years of age.