41 CFR 102-34.155: -34.155 Government motor vehicle identification exemptions.

(a) The head of the agency or designee may authorize a limited exemption to the display of U.S. Government license plates and motor vehicle identification upon written certification stating that identifying the motor vehicle would endanger the security of the vehicle occupants or otherwise compromise the agency mission. A limited exemption may last from one day up to three years before recertification is required. Motor vehicles used primarily for investigative, law enforcement, intelligence, or security duties have an unlimited exemption from displaying U.S. Government license plates and motor vehicle identification when identifying these motor vehicles would interfere with those duties. Motor vehicles assigned for the use of the President and the heads of executive departments specified in 5 U.S.C. 101 have special exemptions from the requirement to display motor vehicle identification.

(b) For motor vehicles that are exempt from motor vehicle identification requirements, display the regular license plates of the State, Commonwealth, territory or possession of the United States, or the District of Columbia, where the motor vehicle is principally operated.