Employers in Colorado are receiving mixed messages about how to deal with employees who use marijuana, according to NPR. Recreational use of marijuana is now legal for adults in both Colorado and Washington state.

Under Colorado state law, employers can ban use of marijuana at work. Another state law prohibits employers from dismissing workers for engaging in lawful activities off the premises of the business during nonworking hours.

In April, an appellate court in Colorado ruled employees can be fired for testing positive for marijuana. The case was filed by Brandon Coats, who was fired by Dish Network in 2010 after he tested positive for marijuana—a violation of company policy. Coats is a quadriplegic, and has a state-issued medical marijuana license. He said he never used marijuana on the job, and argued Dish Network’s policy violated a state law that bans companies from firing employees for off-duty, lawful activities.

The court ruling affirmed a lower court decision that marijuana use does not qualify as lawful because it is still illegal under federal law. Coats’ case is now before the Colorado Supreme Court.

“If you had a martini on Saturday night, or smoked pot on Saturday night, but you’re fine on Monday morning, how is Saturday night the employer’s business?,” said Coats’ attorney, Michael Evans.

The most commonly used urine test used in employer drug testing measures the presence of marijuana’s psychoactive ingredient, THC, which can stay in the body for days, weeks or longer, the article notes. A positive marijuana test does not necessarily indicate a person is high, or has used the drug recently, according to the article.

Barry Sample, Director of Science and Technology for Quest Diagnostics, which conducts drug testing, says eventually there may be tests that measure marijuana intoxication that are similar to Breathalyzers used to detect recent alcohol use. “It might be possible at some point, but it’s still developing,” he said.