My question involves labor and employment law for the state of: FLORIDA

My husband was hired by a Naval Defence Contrat company called ITT at the time of being hired he had NO Convictions on his record. He cleared his backround check with no problem. He was with the company for a few months and got into some trouble. He was conviced of a Felony. and Given just 3 years probation. He Let his Boss and the HR dept. at his job know right away. It has now been over a year later and he was asked to fill out paper work for a Public Trust Security Clearance. The department of the Navy advised that he could not obtain a clearance and he was fired. I have went over every shred of paper work that my husband signed and nothing states that he has to have a clearence, also. His job discription states "No Security Clearance Required" I understand that florida is an At will state, but can they just fire him and the reason be that he can't get a clearence when nothing he signed says he has to have one? Any info would help Thanks.