If you did not have a written employment contract guarantying your employment (example: a one-year written contract which has not yet expired) you were an employee at will and could be terminated for any reason whatsoever--including a suspicion that you used drugs (even if the test may not have followed standard procedures). There is also NO obligation on employers to offer counseling or rehab or any other medical/psychological service: your employer is your employer, not your guardian or medical care provider. (Unless, that is, you had a written contract stating that in the event of positive drug test results, they would offer you rehab, etc.)
Without an employment contract, therefore, you most likely have no recourse.
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