As an at will employee, your employer can terminate you for no reason, a good or bad reason, fair or unfair reason, factually correct or incorrect reason. Your protections are under laws of discrimination, and a variety of other statutes. Your facts would not likely support a claim against the employer if it believed the supervisor who accused you of theft; even if the claim was wrong. Its nice that they are asking you to return to work; many do not even go that far. As for being fired while in jail, there is no law against it. As for the supervisor, you may have a claim against him for defamation, etc.