Americans have spoken loud and clear on the issue of the fraudulent, monstrously destructive prohibition.  They said "END IT."   -   When we legalized marijuana, we CERTAINLY didn't mean "except consumers don't have a right to work!"

The potential "impairment" is minuscule to negligible anyway.  -  Marijuana is not alcohol.   The preponderance of the research shows marijuana is NOT a significant cause of auto accidents.  In 2015, the Drug and Alcohol Crash Risk report produced by the Department of Transportation's National Highway Traffic Safety Administration, found that "while drunken driving dramatically increased the risk of getting into an accident, there was NO evidence that using marijuana heightened that risk."

If an employee were to consume marijuana at work and become impaired, it would be obvious to any decent manager.  -  The REAL reason for employer resistance to justice is many just don't want to hire "those" people.

Shame on these Neanderthal employers!