21.5. No employer may, by reason of the fact that his employee avails himself of his right to a leave under section 21.1, dismiss, lay off, suspend, demote or transfer him or give him less favourable conditions of employment than he is entitled to, particularly by subtracting the leave from his period of vacation.
The first paragraph does not prevent an employer from dismissing, laying off, suspending, demoting or transferring an employee or changing his conditions of employment for a just and sufficient cause, the proof of which is incumbent on him.