Unless your father has specific work duties as outlined in an employment contract or union agreement, then his treatment is legal. The fact is that an employer can set the conditions of work much as they see fit. The only exception would be if an employee's treatment constitutes some form of legally actionable discrimination. Accordingly, if your father's situation is the result of age discrimination (that is he is receiving unfavorable treatment because he is over 40), then he would have a claim. Otherwise, his only recourse is to either accept the situation, complain about it but risk termination, or quit.