A Practice Note discussing employment law issues arising from the legalization of marijuana use for medicinal and recreational purposes in Colorado. This Note also provides best practices for private employers implementing or updating drug testing and drug-free workplace policies. It covers federal and Colorado laws. This Note applies only to private workplaces that are not subject to the federal Drug-Free Workplace Act of 1988. Local law may impose additional or different requirements, but this document is useful and relevant to employers throughout the state.