49 CFR § 382.213 - Controlled substance use.
(a) No driver shall report for duty or remain on duty requiring the performance of safety sensitive functions when the driver uses any drug or substance identified in 21 CFR 1308.11 Schedule I.
(b) No driver shall report for duty or remain on duty requiring the performance of safety-sensitive functions when the driver uses any non-Schedule I drug or substance that is identified in the other Schedules in 21 CFR part 1308 except when the use is pursuant to the instructions of a licensed medical practitioner, as defined in § 382.107, who is familiar with the driver's medical history and has advised the driver that the substance will not adversely affect the driver's ability to safely operate a commercial motor vehicle.
(c) No employer having actual knowledge that a driver has used a controlled substance shall permit the driver to perform or continue to perform a safety-sensitive function.
(d) An employer may require a driver to inform the employer of any therapeutic drug use.
The following state regulations pages link to this page.