Can we have a policy that prohibits all employees from having a detectable amount of marijuana in their system because marijuana is illegal under federal law?

Having a blanket policy is problematic because of state marijuana laws. The federal government allows states to regulate possession of small amounts of marijuana. In some cases, a state law may prohibit you from taking action on the basis of a positive test for marijuana.

In all states, an employer can prohibit employees from using or possessing marijuana at work or from being impaired by the drug at work.

In states where marijuana remains illegal, an employer could take action based on a positive drug test for marijuana.

In states where marijuana has been legalized for medical use, a state law may prohibit employers from taking action based on a positive test for marijuana. In addition, some states place restrictions on actions that can be taken based on a positive test for recreational marijuana.

In all situations, employees who are regulated under federal DOT regulations cannot be allowed to test positive for marijuana. An employer can take action when a regulated employee tests positive.