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

(3) is erroneously regarded as engaging in such use, but is not engaging in such use;

except that it shall not be a violation of this chapter for a covered entity to adopt or administer reasonable policies or procedures, including but not limited to drug testing, designed to ensure that an individual described in paragraph (1) or (2) is no longer engaging in the illegal use of drugs; however, nothing in this section shall be construed to encourage, prohibit, restrict, or authorize the conducting of testing for the illegal use of drugs.