Employee Drug Testing for Marijuana After AB 2188: What California Employers and Workers Need to Know

California’s Assembly Bill 2188 reshaped the rules employers must follow when testing applicants and employees for marijuana. The law, effective January 1, 2024, protects employees’ off-duty cannabis use by limiting the kinds of tests employers may rely on and carving out important exemptions where testing remains permissible. Below is a practical guide explaining when employers can and can’t test for marijuana, the key exceptions under state and federal law, what employers may do after different kinds of test results, and the remedies available to employees who are mistreated in violation of the law.

If you are a Bay Area employer or employee looking to enforce your authority or protect your rights regarding drug testing in the workplace or other employment practices, contact attorney Richard Koss to speak with an experienced and knowledgeable San Francisco employment law attorney.

Overview of AB 2188 and its core rule

AB 2188 adds a new prohibition on discrimination based on off-duty cannabis use and restricts employer use of tests that only detect non-psychoactive cannabis metabolites (the long-lasting breakdown products found by urine or hair tests). In short, employers generally may not take adverse employment action based solely on test results that show prior cannabis use (i.e., non-psychoactive metabolites), because those results do not reliably show current impairment. The law’s focus is on impairment at work, not private, lawful cannabis use away from the workplace.

When employers may still test for marijuana

AB 2188 does not ban all marijuana testing. There are several important exceptions where testing remains lawful:

Federal requirements and contracts

Employers subject to federal law, including many federal contractors and jobs requiring a security clearance or federal background check, remain governed by federal testing rules and may continue to require cannabis testing where federal law or contract terms demand it. DOT-regulated safety-sensitive employees (commercial drivers, transit workers, pilots) remain subject to Department of Transportation testing rules. State law expressly preserves these federal obligations.

Certain safety-sensitive or construction trades exemptions

The statute contains a limited exemption for certain building and construction trades where employers can require testing in specified circumstances; California agencies and practice guidance outline how that exemption operates. Employers in high-risk, safety-sensitive roles should confirm whether an exemption applies to their workforce.

Tests that detect only current impairment

AB 2188 permits employers to use tests that measure psychoactive THC or other indicators of recent intoxication (i.e., tests that reliably indicate current impairment rather than past use). However, reliable, easily administered impairment tests for marijuana are far less developed than alcohol breath tests, and many commonly used assays (urine, hair) detect metabolites only and therefore are not compliant with adverse-action decisions under the new law.

What kinds of tests are effectively prohibited for adverse decisions?

Under AB 2188, adverse employment consequences generally cannot be based solely on hair or urine screens that detect non-psychoactive cannabis metabolites. Those tests show prior use over days or weeks, not whether the individual was impaired on the job. Employers should assume urine and hair results are insufficient to establish impairment for most employment decisions unless a statutory exception applies.

What can an employer lawfully do after a test?

If an employee’s test is negative for recent psychoactive THC or there is no evidence of impairment, the employer has no lawful basis under AB 2188 to discipline or fire the employee for off-duty cannabis use. If an employee’s test or credible workplace observations show current impairment at work, an employer may take disciplinary action consistent with safety and performance policies.

Where federal rules or an applicable exemption apply, employers retain broader testing and discipline rights consistent with those requirements. Employers should document observed unsafe conduct, follow written policies, and consult counsel before acting on ambiguous test results because long-lasting metabolites complicate causation.

Employee rights and remedies

Employees who believe they were disciplined, passed over, or terminated because of lawful off-duty cannabis use generally have remedies under California law. The Department of Fair Employment and Housing (now the Civil Rights Department) enforces the prohibition on discrimination for off-duty cannabis use and provides guidance on what employers may and may not do. A worker who believes an employer violated AB 2188 may file a complaint with the state agency and may have civil remedies in court depending on the facts. Retaliation or disparate treatment claims also remain viable if an employer treats cannabis use as a pretext for unlawfully targeting certain employees, such as those protected from discrimination based on age, race, religion, sex/gender, or other protected characteristics.

How federal law interacts with AB 2188

Federal supremacy means federal testing requirements (DOT, federal contractors, security clearances) can preempt parts of state law for covered employees. AB 2188 explicitly preserves federal obligations, so employers who must follow federal testing rules should continue to do so, even if state law provides broader protections to other workers. For private employers not subject to federal mandates, California’s AB 2188 is the controlling authority. Federal guidance about drug-free workplace programs and protections (e.g., SAMHSA guidance, ADA limits on discrimination of recovering users) remains relevant, especially where an employee’s marijuana use implicates disability protections or rehabilitation. Consult federal resources for those nuances.

Practical steps for employers

Employers should update policies and practices now if they haven’t already: revise drug-testing policies to focus on impairment, remove reliance on hair or urine metabolite tests for adverse action where AB 2188 applies, train supervisors to document actual workplace impairment or unsafe conduct, and identify any federal or construction-trade exemptions that apply to their workforce. Legal counsel can help craft compliant testing protocols and revise employee handbooks to reflect the new landscape.

Contact Attorney Richard Koss for Help With Employment Issues and Discrimination in Your San Francisco Workplace

Employees who believe their rights under AB 2188 were violated can seek relief through the state Civil Rights Department or the courts. Because the science of impairment testing for marijuana is still evolving and the legal interplay with federal rules can be complex, employers and employees should get specific legal advice when disputes arise.

For help with employment issues in the San Francisco Peninsula and across the East Bay, contact Bay Area employment law attorney Richard Koss for practical advice and effective assistance.