The Colorado Supreme Court, in a 6-0 decision, has held that an employer’s right to fire employees for failing drug tests trumps state laws permitting marijuana use. Under the Court’s ruling, even employees using prescribed medical marijuana off-duty can still be subject to termination.

The case arose from the firing of Brandon Coats, a quadriplegic who worked for Dish Network. Colorado permits marijuana use for medical purposes, and Coats was prescribed it to treat muscle spasms. Coats used the drug off duty. He was fired in 2010 following a failed drug test and subsequently sued. Dish Network was initially successful at both the trial and appellate levels, and the case was heard by the Colorado Supreme Court in September.

At issue was whether the drug, which is illegal at the federal level, is nonetheless considered “lawful.” Under Colorado’s “Lawful Activities Statute,” it is illegal for an employer to fire an employee based on the employee’s lawful activities outside of work. Both the trial and appellate courts held Coats’ marijuana use was not a “lawful” activity, a decision echoed by the Supreme Court.

The Court noted that under Colorado’s “Lawful Activities Statute,” the term “lawful” only refers “to those activities that are lawful under both state and federal law. Therefore, those employees who engage in an activity such as medical marijuana use that is permitted by state law but unlawful under federal law are not protected by the statute.”

The decision represents a setback for medical and recreational marijuana proponents and could serve as a guide for other states addressing the increasing legalization of the drug.