A Colorado Supreme Court hearing that will have major implications for marijuana and the workplace ended Tuesday with the state’s most esteemed justices mostly scratching their heads.

The debate topic was this: If it isn’t illegal to use medical marijuana, does that make it a “lawful” activity for which employers can’t fire you?

How the justices answer that question will, for the first time, define whether employers must tolerate medical-marijuana use by their employees and will set whether medical-marijuana patients have any job protection for their cannabis use. The outcome also has implications for recreational marijuana use, which presents similar questions.

In an era of more permissive state laws on marijuana, the justices’ decision could significantly affect whether people take advantage of those laws. An attorney for Brandon Coats, a quadriplegic who was fired for medical-marijuana use and who brought the case, said if the justices rule strictly against patients, “that means our medical-marijuana amendment is really just for the unemployed.”

Vance Knapp, an attorney who is not connected to the case but has followed it closely, said a ruling in favor of Coats could throw employment law “into chaos.”

“This is a hot issue nationally,” Knapp said.

“At a minimum,” Coats’ attorney, Michael Evans, said after the hearing, “I think everyone is going to get clarification.”

For an hour Tuesday morning, Evans and an attorney for Dish Network, the company that fired Coats, sparred over the issue in the state Supreme Court’s ornate downtown chambers. And, repeatedly, the Supreme Court justices interjected with the most basic of questions.

Justice Allison Eid asked both attorneys what they think “lawful” means. Justice Gregory Hobbs questioned the attorney for Dish Network about her definition of “use.” Chief Justice Nancy Rice frequently asked about the simple facts of the case.

“Both counsel are asking us to write a discreet, well-crafted opinion,” Rice said during the hearing. “And I don’t know what happened here.”

That confusion reflected the conflicting jumble of state and federal laws on display during the hearing.

Coats, who has used medical marijuana to control spasms and seizures since a car accident, says he never used nor was impaired on the job. He contends he was fired in 2010 from his job as a Dish Network customer service representative after a cheek-swab drug test revealed inactive THC in his system. Dish Network says it has a zero-tolerance policy against employees using illegal drugs.

Coats challenged his dismissal under a law called the Colorado Lawful Off-Duty Activities Statute. The law protects employees from termination for doing things off-the-clock that are legal.

But that’s where the crux of the case rests: Is medical marijuana, which Colorado voters approved in 2000 but is illegal federally, actually “lawful”?

Two lower courts have said no, and Dish’s attorney, Meghan Martinez, urged the Supreme Court to find the same. She argued that Colorado’s medical-marijuana law, which is in the state constitution, doesn’t guarantee patients the right to use marijuana.

“It is an affirmative defense or it is an exception to state criminal laws,” she said. “It is not a broad right.”

But Evans said he wasn’t trying to argue that Coloradans have a right to marijuana. Doing so, he said, raised the specter of federal pre-emption of Colorado’s entire marijuana regime.

Instead, Evans said the justices should consider only state law in deciding what is lawful under the state’s off-duty activities statute. Other laws prevent employees from using marijuana on the clock or block employees in dangerous occupations from using drugs, he said.

“We believe you can find a way for employers and employees to peaceably coexist,” Evans said.

Some justices seemed skeptical. Justice William Hood said just because the off-duty activities statute doesn’t mention federal law doesn’t mean the legislature didn’t intend for it to be considered.

“It seems like a lot of your argument relies on silence,” he told Evans.

Martinez met similar skepticism when she contended that Coats was actually “using” marijuana on the job because he said he derived medical benefit from cannabis that extended into work hours.

Speaking last, Michael Francisco of the state attorney general’s office, sided with Dish. He said limiting the off-duty activities statute only to Colorado law could bring “absurdities,” such as someone convicted of a crime like federal tax fraud not being able to be fired.

The justices could take weeks to issue a written opinion. Only six of the seven Supreme Court justices will decide that ruling. Justice Monica Márquez, whose father sat on the Court of Appeals panel that upheld Coats’ firing, recused herself. A tie among Supreme Court justices would mean the lower court’s ruling stands.

Outside after the hearing, Coats, who watched the arguments in his wheelchair from the front row, said he was optimistic, although he acknowledged the arguments were tough. Since Dish fired him, he said, he has been unemployed.

“I’ve been having a hard time finding employment,” he said. “I want to work.”

John Ingold: 303-954-1068, jingold@denverpost.com or twitter.com/johningold