There is so much controversy surrounding the feared ROT!! He is a doctor and therefore able to practice as such.
It is generally up to the employer to allege that the ROT is reasonable, valid and thus enforceable. In terms of our constitution, no one should be restricted from carrying on business. Therefore a ROT is invalid in terms of our constitution.
Restraint of trade is not regulated by labour law, because it forms part of an employment contract. Generally the employee is expected to honour the agreement, but again it is up to the person enforcing it to prove that is valid and reasonable.