All personnel actions affecting employees or applicants for employment who are at least 40 years of age (except personnel actions with regard to aliens employed outside the limits of the United States) in military departments as defined in section
102 of title
5, in executive agencies as defined in section
105 of title
5 (including employees and applicants for employment who are paid from nonappropriated funds), in the United States Postal Service and the Postal Regulatory Commission, in those units in the government of the District of Columbia having positions in the competitive service, and in those units of the judicial branch of the Federal Government having positions in the competitive service, in the Smithsonian Institution, and in the Government Printing Office, the Government Accountability Office, and the Library of Congress shall be made free from any discrimination based on age.