49 CFR 28.131 - Illegal use of drugs.
(a) General. (1) Except as provided in paragraph (b) of this section, this part does not prohibit discrimination against an individual based on that individual's current illegal use of drugs.
(2) The agency shall not discriminate on the basis of illegal use of drugs against an individual who is not engaging in current illegal use of drugs and who -
(i) Has successfully completed a supervised drug rehabilitation program or has otherwise been rehabilitated successfully;
(ii) Is participating in a supervised rehabilitation program; or
(iii) Is erroneously regarded as engaging in such use.
(b) Health and rehabilitation services. The agency shall not deny health services or services provided under titles I, II, and III of the Rehabilitation Act to an individual on the basis of that individual's current illegal use of drugs, if the individual is otherwise entitled to such services.
(c) Drug testing. (1) This part does not prohibit the agency from adopting or administering reasonable policies or procedures, including but not limited to drug testing, designed to ensure that an individual who formerly engaged in the illegal use of drugs is not engaging in current illegal use of drugs.
(2) Nothing in paragraph (c) of this section shall be construed to encourage, prohibit, restrict, or authorize the conduct of testing for the illegal use of drugs.