Employer drug testing is governed by state law, and cannabis has made the landscape genuinely complicated.

Testing programs are generally permitted with notice, and are mandatory for safety-sensitive positions in regulated transportation and other federally regulated sectors, where federal rules preempt state protections.

State protections vary widely. Some states prohibit adverse action based on lawful off-duty conduct; some protect registered medical cannabis patients and require accommodation short of on-duty impairment; some protect recreational use outside work; and some provide no protection at all.

Impairment versus presence. Cannabis metabolites persist long after impairment ends, so a positive test does not establish impairment. Several statutes now require evidence of impairment at work rather than a positive test alone, and some restrict pre-employment testing for cannabis entirely.

Reasonable suspicion testing should rest on documented, objective observations by trained supervisors, recorded contemporaneously on a form.

Safety-sensitive designations should be defined by written criteria and applied consistently.

Disability interaction. Current illegal drug use is generally unprotected, but an employee in recovery, or lawfully using prescribed medication, may be entitled to accommodation, and testing that reveals lawful prescriptions raises inquiry and confidentiality obligations.