United States Code
USC most recently checked for updates: Dec 14, 2019
Temporary appointments in the grade of ensign may be made by the President. Each such temporary appointment terminates at the close of the next regular session of the Congress.
Officers in the permanent grade of ensign may be temporarily promoted to and appointed in the grade of lieutenant (junior grade) by the President whenever vacancies exist in higher grades.
When determined by the Secretary to be in the best interest of the service, officers in any permanent grade may be temporarily promoted one grade by the President. Any such temporary promotion terminates upon the transfer of the officer to a new assignment.