"In other states we've seen companies get rid of screenings altogether or modify them significantly because they want to keep employees working for them and respect their right to do what they want in their free time," said Linn. "Who cares if they smoke a joint Friday night and go into work Monday morning, even though they'd fail a drug test?"

It's possible that more companies might stop testing for marijuana use. Some have already made that change following the legalization of medicinal marijuana in Illinois, the widespread use of CBD oil and potential legalization of recreational marijuana, said Dr. David Fletcher, founder of SafeWorks Illinois in Champaign, which does drug testing for employers.

"We've actually had some employers say they don't want to test for it," Fletcher said. "That's kind of the new trend."

Many private companies in Colorado don't test for drugs and most Colorado restaurants have stopped drug testing entirely, said Markie Davis, director of employee benefits and risk management for the state of Colorado, at a recent Chicago program for employers about marijuana legalization.