There's really only one: he gets divorced. Depending on where your friend is living, he may be able to get a civil divorce dissolving his marriage, whether or not the "Syrian Orthodox Church" says he can, or should. I do not know enough about the rules Syrian Orthodox Church to be able to tell you the effect of a civil divorce on his continued membership; he should talk to a clergyman about that.
Other than that, you can't legally and effectively marry him, in any state in the U.S. Going through a marriage ceremony, if you know that you're already married to someone else who's still alive and you haven't divorced, is attempting to commit bigamy, which is a crime in most states, though a rarely prosecuted one. A bigamous marriage is void or voidable, so you're not really legally married to the second "spouse".
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