What is the motor carrier law with regards to regulating overtime pay with Couriers such as FeDex or DHL?

Can the department of labor enforce overtime pay for Couriers for business that deliver and pick up packages. There is no CDL requirements for this type of job . It working for DHL( doing the same things that UPS and Fedex do). Or is there a law stating that the NCDOT has jurisdiction over this type of work and thus exempt from overtime if a salaried employee.