5 CFR 2.1 - Competitive examinations and eligible registers.
(a) OPM shall be responsible for open competitive examinations for admission to the competitive service which will fairly test the relative capacity and fitness of the persons examined for the position to be filled. OPM is authorized to establish standards with respect to citizenship, age, education, training and experience, suitability, and physical and mental fitness, and for residence or other requirements which applicants must meet to be admitted to or rated in examinations.
(b) In addition to the names of persons who qualify in competitive examinations, the names of persons who have lost eligibility on a career or career-conditional register because of service in the armed forces, and the names of persons who lost opportunity for certification or who have served under career or career-conditional appointment when OPM determines that they should be given certification, may also be entered at such places on appropriate registers and under such conditions as OPM may prescribe.
(c) Whenever the Office of Personnel Management (1) is unable to certify a sufficient number of names to permit the appointing officer to consider three eligibles for appointment to a fourth-class postmaster position in accordance with the regular procedure, or (2) finds that a particular rate of compensation for fourth-class postmaster positions is too low to warrant regular competitive examinations for such positions, it may authorize appointment to any such position or positions in accordance with such procedure as may be prescribed by OPM. Persons appointed under this paragraph may acquire competitive status subject to satisfactory completion of a probationary period prescribed by OPM.