If the order of disposition releases the minor to the custody of the minor’s parents, guardian or legal custodian, or continues the minor in such custody, the court may place the person having custody of the minor, except for representatives of private or public agencies or governmental departments, under supervision of the probation office. Rules or orders of court shall define the terms and conditions of protective supervision, which may be modified or terminated when the court finds that the best interests of the minor and the public will be served thereby.