VERY tough call on the available facts.
In general, an employer may give whatever information is factually true or - and this is the kicker - HONESTLY BELIEVED BY THE EMPLOYER TO BE TRUE. Many, many states, and I specifically include Florida in this, have statutes indemnifying the employer from any damages caused by this.
HOWEVER. Again, I specifically include Florida statutes when I say that if the employer KNOWS the information to be false, or if it is given in such a way as to be misleading or malicious, it is not protected.
You do not say why you left. If you left voluntarily and the employer is lying in his teeth saying that he fired you for stealing, that's not protected and you do indeed have legal recourse. However, if he did indeed fire you for stealing and he honestly believes you to be guilty EVEN IF HE IS WRONG he is entitled to his opinion and to express it. Finally, if you left voluntarily and later facts were uncovered to lead him to believe you had been stealing, he is legally allowed to say so. The same applies if you really were stealing from him. I'm not for a moment suggesting that this is the case - I'm just using an example.
He may NOT maliciously and deliberately try to mislead prospective employers; his statements are only protected if he honestly and truly believes them to be the case. He does not have to be correct; he only has to be telling the truth as he sees it.
If you need further assistance please post again.