20 U.S.C. § 9578

(a) In general The Director may appoint, for terms not to exceed 6 years (without regard to the provisions of title 5 governing appointment in the competitive service) and may compensate (without regard to the provisions of chapter 51 and subchapter III of chapter 53 of such title relating to classification and General Schedule pay rates) such scientific or technical employees to carry out the functions of the Institute or the office, board, committee, or center, respectively, if— (1) at least 30 days prior to the appointment of any such employee, public notice is given of the availability of such position and an opportunity is provided for qualified individuals to apply and compete for such position; (2) the rate of basic pay for such employees does not exceed the maximum rate of basic pay payable for positions at GS–15, as determined in accordance with section 5376 of title 5 , except that not more than 7 individuals appointed under this section may be paid at a rate that does not exceed the rate of basic pay for level III of the Executive Schedule; (3) the appointment of such employee is necessary (as determined by the Director on the basis of clear and convincing evidence) to provide the Institute or the office, board, committee, or center with scientific or technical expertise which could not otherwise be obtained by the Institute or the office, board, committee, or center through the competitive service; and (4) the total number of such employees does not exceed 40 individuals or ⅕ of the number of full-time, regular scientific or professional employees of the Institute, whichever is greater. (b) Duties of employees All employees described in subsection (a) shall work on activities of the Institute or the office, board, committee, or center, and shall not be reassigned to other duties outside the Institute or the office, board, committee, or center during their term.