Section 199.103 - Use of persons who fail or refuse a drug test(a) An operator may not knowingly use as an employee any person who-(1) Fails a drug test required by this part and the medical review officer makes a determination under DOT Procedures; or(2) Refuses to take a drug test required by this part.(b) Paragraph (a)(1) of this section does not apply to a person who has-(1) Passed a drug test under DOT Procedures;(2) Been considered by the medical review officer in accordance with DOT Procedures and been determined by a substance abuse professional to have successfully completed required education or treatment; and(3) Not failed a drug test required by this part after returning to duty.53 FR 47096, Nov. 21, 1988, as amended by Amdt. 199-2, 54 FR 51850, Dec. 18, 1989. Redesignated and amended by Amdt. 199-19, 66 FR 47118 , Sept. 11, 2001