Generally speaking, an employer is at liberty to terminate an at-will employee for any reason or no reason at all, unlawful discrimination or retaliation excepted. Generally speaking, an employer who terminates an at-will employee under the mistaken belief that the employee has been using illegal drugs is legally free to do so. Nothing says the employer has to be right, or to act fairly or wisely. Employers are free to be wrong and do stupid and unfair things so long as they do not violate the law. Employees in a unionized workplace may have more rights under their collective bargaining agreement. If you are in a union, consult your shop steward or union representative without delay.
(My analysis would be different if you had a disability, such as cerebral palsy, that affected your speech in such a way that your employer thought you were under the influence of drugs. But you say nothing of the sort so I will not infer such a circumstance.)
Not legal advice as I don't practice law in Alabama. It's just my two cents on the facts you describe in light of general principles of law. If you need legal advice, please consult a lawyer who holds Alabama licensure. That's not me as I practice in Vermont ONLY.
As suggested in the prior answer, Alabama is an "at-will" employment state. You can be terminated for a good reason, bad reason or no reason at all, so long as the reason is not discriminatory (race, age, sex, etc.) protected by Federal discrimination laws. I don't believe that a termination based upon a mistaken belief in your use of drugs is a protected catagory that would give rise to a discrimination claim. The outcome of the unemployment compensation matter is not outcome determinative on the termination issue. So just because you are receiving your unemployment compensation is not evidence of a discriminatory intent by the employer. The two different answers on the reason for the termination is a possible area of inquiry, but if neither reason articulated is discriminatory, then not actionable I would imagine.
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