The validity of a marriage can be challenged by the contestant spouse through an action for nullity. Any subsequent marriage entered into by a married person with any person who is not their husband or wife is bigamous, and is considered “illegal and void from the beginning” under California law [Fam. C. § 2201(a)]. The innocent spouse may obtain relief through a nullity proceeding, where he/she would present evidence that their spouse is still validly married to another at the time of their marriage. Unlike a dissolution action which aims to terminate a valid marriage, an action for nullity inquires on whether such marriage actually existed (in this case, on the grounds of an existing prior marriage).
The action for nullity generally takes a distinct and different course than an action for dissolution of marriage, which is why it is advisable to work with a lawyer who is an expert in annulment proceedings.