What are the rules to be followed in promoting employees, give sample of illegal holding of appointments?

i want to know what are the illegalities being committed if someone tries to block or delay the appointment of an employee for a position he is qualified. how long is it for an appointment to take effect or is there a time frame required by law to consider an appointment effective? cite provisions on the labor code that deals with this

Important to distinguish if the employer is private, federal, or what. That determines the law that governs the case.

Generally, the employer doesn't HAVE to promote anyone, being qualified is not a guarantee. If others are being promoted while plaintiff is not, then questions have to be raised about why. If race, religion, etc. are involved, then this can be an actionable issue. If the employee has dings on his/her record then it can be hard to prove discrimination. Employers have a right to make judgment calls about employees and their promotions.