Section 120.17 - Use of prohibited drugs(a) Each employer shall provide each employee performing a function listed in subpart E of this part, and his or her supervisor, with the training specified in that subpart. No employer may use any contractor to perform an air traffic control function unless that contractor provides each of its employees performing that function for the employer, and his or her supervisor, with the training specified in subpart E of this part.(b) No employer may knowingly use any individual to perform, nor may any individual perform for an employer, either directly or by contract, any air traffic control function while that individual has a prohibited drug, as defined in this part, in his or her system.(c) No employer shall knowingly use any individual to perform, nor may any individual perform for an employer, either directly or by contract, any air traffic control function if the individual has a verified positive drug test result on, or has refused to submit to, a drug test required by subpart E of this part and the individual has not met the requirements of subpart E of this part for returning to the performance of safety-sensitive duties.(d) Each employer shall test each of its employees who perform any air traffic control function in accordance with subpart E of this part. No employer may use any contractor to perform any air traffic control function unless that contractor tests each employee performing such a function for the employer in accordance with subpart E of this part.Doc. No. FAA-2008-0937, 74 FR 22653, May 14, 2009; Amdt. 120-0A, 75 FR 3153, Jan. 20, 2010