Employers in states where marijuana is legal for medicinal or recreational use must decide how to handle employees who use the drug when they are not on duty, USA Today reports.

Some workers in Colorado and Washington state, where recreational marijuana use is legal, say they are being punished for using the drug when they aren’t on the job. Employers say they are trying to maintain drug-free workplaces, the article notes.

“I imagine there will be a great deal of upheaval in the future. The law is going to be in flux for another 10 years,” said Curtis Graves, a staff attorney with the Mountain States Employers Council, which advises companies on workplace issues.

In the 20 states that allow medical marijuana, employers do not have to allow any kid of marijuana use in the workplace. In Colorado, workers cannot be fired for legal activities while they are off duty. However, the state’s courts have also ruled marijuana is not lawful, because the federal government still considers it illegal.

A growing number of employers in Colorado are testing prospective employees before hiring, and are continuing to perform random drug testing, according to Tiffany Baker, co-owner of the Denver DNA and Drug Center, which provides drug-testing services to employers. “I think big companies were already testing anyway,” she said. “I think small companies are … now more likely to send their workers over.”

In Washington state, manufacturers and companies working in federally regulated areas, such as the aerospace industry, have long tested job applicants for drug use. Jennifer Lambert, a vice president of the employment agency Terra Staffing Group, says these employers are continuing to test job applicants for drugs. “It’s sort of a Wild West scenario. It’s very, very tricky,” she said. “I feel badly when someone comes to us and doesn’t understand the implication of their pot smoking.”