45 C.F.R. § 73.503
(a) Participation in political activities while on duty, in uniform, in any room or building occupied in the discharge of official duties or using a Federal vehicle; prohibition. An employee covered under this subpart may not participate in political activities:
(4) While using a Government-owned or Government-leased vehicle or while using a privately owned vehicle in the discharge of official duties.
Example 1 to paragraph (a):A covered employee who uses the employee's privately owned vehicle on a recurrent basis for official business may place a partisan political bumper sticker on the vehicle, as long as the bumper sticker is covered while the vehicle is being used for official duties.
Example 2 to paragraph (a):A covered employee who uses the employee's privately owned vehicle on official business must cover any partisan political bumper sticker while the vehicle is being used for official duties if the vehicle is clearly identified as being on official business.
Example 3 to paragraph (a):A covered employee who uses the employee's privately owned vehicle only on an occasional basis to drive to another Federal agency for a meeting, or to take a training course, is not required to cover a partisan political bumper sticker on the vehicle.
Example 4 to paragraph (a):A covered employee may not place a partisan political bumper sticker on any Government-owned or Government-leased vehicle.
Example 5 to paragraph (a):A covered employee may place a bumper sticker on the employee's privately owned vehicle and park the vehicle in a parking lot of an agency or instrumentality of the United States Government or in a non-Federal facility for which the employee receives a subsidy from the employing agency or instrumentality.
Example 6 to paragraph (a):A covered employee may not wear partisan political buttons or display partisan political pictures, signs, stickers, or badges while the employee is on duty or at the place of work.
(e) Participation in political organizations; prohibitions. An employee covered under this subpart may not:
(f) Participation in political fundraising; prohibitions. An employee covered under this subpart may not:
(g) Participation in political campaigning; prohibitions. An employee covered under this subpart may not:
(h) Participation in elections; prohibitions. An employee covered under this subpart may not: