California Code, Penal Code - PEN § 281

(a) Every person having a spouse living, who marries or enters into a registered domestic partnership with 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 or registered domestic partnerships by the register, certificate, or other record evidence thereof, but the marriages or registered domestic partnerships may be proved by evidence which is admissible to prove a marriage or registered domestic partnership in other cases; and when the second marriage or registered domestic partnership 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.