Americans with Disabilities Act (ADA) of 1990 (with amendments issued through 2008)

(d) "Illegal use of drugs" defined

(1) In general

The term "illegal use of drugs" means the use of drugs, the possession or distribution of which is unlawful under the Controlled Substances Act (21 U.S.C. 801 et seq.). Such term does not include the use of a drug taken under supervision by a licensed health care professional, or other uses authorized by the Controlled Substances Act or other provisions of Federal law.

(2) Drugs

The term "drug" means a controlled substance, as defined in schedules I through V of section 202 of the Controlled Substances Act (21 U.S.C. 812).