La. Stat. tit. 17 § 543
Whenever an employee who has acquired permanent status, as set forth in R.S. 17:541 and R.S. 17:542, is promoted by moving such employee from a position of lower salary to one of higher salary, such employee shall serve a probationary period in the higher position before acquiring permanent status therein, but shall retain the permanent status acquired in the lower position from which he or she was promoted.
During the probationary period in the position to which promoted an employee shall not be disciplined, removed or demoted to the lower position from which he or she was promoted except in compliance with the provisions of R.S. 17:541. At the expiration of the probationary period in the higher position, an employee, unless removed or demoted in accordance with R.S. 17:541, shall automatically acquire permanent status in the higher position and thereafter may not be disciplined, removed or demoted from such higher position except in compliance with the provisions of R.S. 17:542.
Where an employee has not completed the probationary period for employees as required by R.S. 17:541, or for a particular promotional position as established herein, and is promoted to a higher position, the probationary period shall continue to run and at the end of such three-year probationary period the employee shall automatically acquire permanent status in the previously held position until permanent status in the new positions acquired by compliance with the provisions of this Section. All employees shall be given credit for time served in employment in their capacity as such.
La. R.S. § 17:543