28 CFR Part 36 Nondiscrimination on the Basis of Disability by Public Accommodations and in Commercial Facilities (1991 ADA Title III Regulations)

(c) Drug testing. 

(1) This part does not prohibit a public accommodation 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 now engaging incurrent illegal use of drugs.

(2) Nothing in this paragraph (c) shall be construed to encourage, prohibit, restrict, or authorize the conducting of testing for the illegal use of drugs.