CAL. PEN. CODE § 281 : California Code - Section 281

(a) Every person having a husband or wife living, who marries any other person, except in the cases specified in Section 282, is guilty of bigamy.

(b) Upon a trial for bigamy, it is not necessary to prove either of the marriages by the register, certificate, or other record evidence thereof, but the marriages may be proved by evidence which is admissible to prove a marriage in other cases; and when the second marriage took place out of this state, proof of that fact, accompanied with proof of cohabitation thereafter in this state, is sufficient to sustain the charge.