Under California law. your marriage would be null and void if he was still married to somebody else at the time of your marriage. He also committed the crime of bigamy.
Even so, I wouldn't just walk away without some legal help to clean up the mess
California law does not recognize common law marriage, where a man and woman who live together for a specified period of time and hold themselves out as husband and wife are considered legally married. However, if you lived with your ex-not-really-your-husband in a common law marriage state long enough to qualify, you might be considered married under that state's law.
If you had any sort of joint assets or debts, you should also get some legal help with that issue. I would talk to a family law attorney who is also familiar with Nevada law.
Please understand that this is a general discussion of legal principles by a California lawyer and does not create an attorney/client relationship. It's impossible to give detailed, accurate advice based on a few sentences on a website (and you shouldn't provide too much specific information about your legal matter on a public forum like Avvo, anyway). You should always seek advice from an attorney licensed in your jurisdiction who can give you an informed opinion after reviewing all of the relevant information.
You cannot walk away from it or remarry without problems. Even though as Mr.Marshall says your marriage is null and void, which means it never existed, to the outside world it appears as if you are married. You want to clear this up to avoid liability for his debts and to obtain your share of any jointly held assets. Your address says Oakland. You may be able to file a petition for an annulment from CA. If so it is simple and quick. See the Family Law Facilitator at the Family Court in Oakland.
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