The possession, distribution, and use of cannabis remains illegal under federal law. Consequently, in isolation, employers may believe that enforcing their zero-tolerance policies for drug use (as referenced here, zero-tolerance refers to policies that prohibit any on-duty or off-duty use of unlawful cannabis products) remains a defensible position, including in response to employee complaints that such policies restrict employees’ otherwise permissible use of cannabis products. But how does state legalization of recreational and medical cannabis…