The above incident shows how normal citizens may unwittingly commit bigamy. This man legitimately believed that his casino wedding had no legal basis, and this is an understandable point of view in many ways. In order to get married in Mississippi, you need to go through a lengthy process to get a marriage license from a court, which takes at least 24 hours.
The exact wording of the law against bigamy suggests that intent is important. In order to commit bigamy, you have to actually be aware of what you are doing. On the one hand, the man might be able to argue that he was not of sound body and mind when he committed to the first marriage, having been heavily intoxicated at the time. He might also argue that he had a reasonable belief that this marriage was not legally binding.