Return to Duty means somebody failed a drug or alcohol test and they need to get back to work now. This means a couple of different things, for example; If an employee is regulated by the DOT (Department of Transportation) as a commercial truck driver by someone with a CDL (Commercial Driver’s License), you can fire him if he fails a test but he still has to complete the DOT-mandated or return to duty process which we will talk about in a second.