Yes. Legal rules vary from state to state where marijuana is now legal for recreational use. Also, as marijuana stays in the system over a prolonged period of time, the employee may use marijuana legally, but be drug tested at a later time and lose their job. In general, according to Law360, marijuana legalization laws in states where it is legal support employers in drug testing for marijuana use and firing people for it. Marijuana use is still illegal under federal law, and many employers prefer to maintain their drug-free workplace policies.