Can employers drug test in states where marijuana is legal?

Legalization of recreational and medical use of marijuana varies from state to state and this is constantly changing. Since marijuana is still a prohibited Schedule I substance at the federal level, employers can enforce a zero-tolerance standard and still prohibit marijuana use, possession, and impairment in the workplace, on job sites, during working hours or when employees are on call in order to ensure a safe work environment. Some states may be building employee and employer protections into their legislation and PlusOne will amend its processes as laws dictate.