At the time of this writing, 33 states and the District of Columbia have legalized the medical use of marijuana, and 10 of those states plus DC have passed laws decriminalizing recreational use. This creates myriad challenges for employers, especially when facing an already-shrinking talent pool.

Complex intersection. For employers and recruiters, the issue is further complicated by the fact that marijuana remains illegal at the federal level while the state laws vary considerably in how they address the intersection of legalized marijuana and employment law. Some states specifically provide prohibitions against employment discrimination for medical marijuana use, while others provide protection from adverse employment actions. The case law is diverse and a work in progress.

The result of these legal conflicts is particularly challenging for companies that span jurisdictions.

At-work use. So far, neither the courts nor any statute has mandated that employers accommodate or permit use of marijuana at work or while working. Employers do not have to tolerate an employee's impairment while at work. Because cannabis is stored in fat cells and can remain in the system for weeks or months, drug testing for impairment determination is unreliable. Therefore, marijuana impairment is observational, unlike alcohol, which can be tested to show recent ingestion.

Workers' comp. Among the most pressing questions is what to do about employees who carry a medical marijuana card and have an on-the-job accident and test positive for marijuana. Are they disqualified from workers' compensation as would be those employees testing positive for alcohol or other illegal drugs?

Relatedly, what about the employee who is injured and prescribed medical marijuana because of that injury? Will the workers' compensation carrier pay for that prescription?

Employers also face questions about the need to accommodate the use of medical marijuana. A court in Arizona held that an employer violated the state medical marijuana statute when it terminated a legal user of medical marijuana for a positive drug test without any proof she was impaired while on the job.

In order to expand the number of available candidates, some employers are no longer testing for marijuana use except for safety-sensitive jobs. Still, it's wise to make clear that working while under the influence — and marijuana use at work or during the work day — is strictly prohibited.

The ADA. The federal Americans with Disabilities Act seems simpler. The most recent consensus is that having an interactive conversation with the employee can never be wrong, and that ADA accommodations relate to the underlying medical condition and not to the use of the medical marijuana. In this analysis, the use of medical marijuana is the specific accommodation requested, but there may be other accommodations the company can and will do, even if the use of marijuana is not one of them. Sometimes other medications that are not illegal may work.

So what's an employer to do? The short answer: Know the applicable state law. Review your employment policies, including drug testing policies (keeping in mind new OSHA regulations regarding post-accident testing).

Some employers are adopting a zero-tolerance policy — especially in safety-sensitive positions. When adopting such a policy, be careful how you draft it. Simply prohibiting the use of illegal drugs is not enough because in many states, cannabis use is legal. (Note that federal contractors must require and adopt a policy consistent with federal law.)

Consider using a medical review officer to assess employees testing positive for use of medical marijuana. This allows you to have a qualified third party assess the underlying medical condition and make a recommendation as to safety.

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