5 USC 3394 - Noncareer and limited appointments

(a) Each noncareer appointee, limited term appointee, and limited emergency appointee shall meet the qualifications of the position to which appointed, as determined in writing by the appointing authority.
(b) An individual may not be appointed as a limited term appointee or as a limited emergency appointee without the prior approval of the exercise of such appointing authority by the Office of Personnel Management.