Trevor Hughes

USA TODAY

DENVER — In a closely watched court case with potential national implications, Colorado's highest court is considering whether an employee can be fired for using marijuana outside of work.

DISH Network in 2010 fired call-center worker Brandon Coats after he tested positive for marijuana. Coats, who is partially paralyzed and uses a wheelchair, says he never hid his off-duty medical marijuana use from his bosses. Instead, he argues, his three years of outstanding performance show he was a responsible worker who used pot nightly to help control seizures and spasms.

DISH argues Coats violated the company's zero-tolerance drug policy, and says he was treated no differently than an employee who showed up drunk. The two sides made oral arguments before the Colorado Supreme Court on Tuesday.

Part of the problem is that detectable levels of marijuana can remains in a user's system for more than a month after consumption, long after the intoxicating effects have passed. If the state Supreme Court upholds lower court rulings, it could strip away any protections workers may have for using a legal substance in Colorado.

"If I can fight this fight in order to change that, that's what I'll do," Coats said outside of court Tuesday.

Coats brought his lawsuit against the company under Colorado's lawful off-duty activities law, which specifically says employers cannot fire people for doing something legal on their own time. The law originally protected cigarette smokers, among others, and predates the state's legalization of marijuana.

But now Coats is asking the court to consider whether marijuana use, be it medical or recreational, is "lawful" in Colorado. A decision either way could have wide-ranging implications for marijuana users and employers across the country.

Twenty-three states and the District of Columbia have legalized some form of medical marijuana use, and Colorado and Washington states also have legalized recreational use. Marijuana remains illegal under federal law and employment expert Curtis Graves of the Mountain States Employers Council said that until federal law changes, employees have few protections for using pot if their employers object.

"The writing's on the wall: I suspect that within a few years, marijuana is going to make that transition and be treated like alcohol, and employers are going to have to deal with it. At some point, we're going to have to come up with a better scheme," he said. "This case will settle it, but it will only be temporary."

DISH attorneys argue that since Coats knew about the zero-tolerance policy and still came to work with pot in his system, they had the right to fire him. They also argue that since marijuana remains illegal at the federal level, he deserves no special protection.

"It doesn't matter if he's impaired or not," said DISH attorney Meghan Martinez. "Medical marijuana is not lawful in Colorado … therefore it cannot be a lawful activity."

The Colorado Attorney General's office has sided with DISH.

After the hearing, Coats' attorney, Michael Evans, said the confusion over whether federal or state law takes precedence when state voters have specifically legalized pot needs clarification. Evans asked the court to consider that Coats was working in a non-hazardous, non-executive position for a Colorado-based company, and that no one ever accused him of being impaired on the job.

"We're getting very confusing and mixed messages from everywhere," Evans said. "We know this is not going away. We need to get this clarified. Let's not put our head in the sand, and (let's) deal with this reasonably."

The court took the oral arguments under advisement and will issue a written ruling later.