I was thinking that he might have grounds for annulment of the marriage if it was based on fraud. If he decides to legally annul the marriage then he is free to remarry because he was never legally married. Marriage is defined by the state not the congregation so if they say it is invalid then it is not valid. It reminds me of the crazy "vow of faithfulness" that is allowed for JW couples to cohabit when divorce is not allowed by the state yet the circumstances for a JW scriptural divorce are met. It basically says "we will get married when we are allowed to but until then we can live like we are married without any congregational consequences".
Whatever he decides to do he will have to live with his decision and the consequences. I hope he thinks seriously about his options and his reasoning.