Mont. Code Ann. § 39-2-210
39-2-210 Limitation on adverse action
39-2-210 . Limitation on adverse action. Except as provided in 16-12-108 , no adverse action, including followup testing, may be taken by the employer if the employee presents a reasonable explanation or medical opinion indicating that the original test results were not caused by illegal use of controlled substances or by alcohol consumption. If the employee presents a reasonable explanation or medical opinion, the test results must be removed from the employee's record and destroyed.