(a) The use of force, but not deadly force, against a child younger than 18 years is justified:
(1) if the actor is the child's parent or stepparent or is acting in loco parentis to the child; and
(2) when and to the degree the actor reasonably believes the force is necessary to discipline the child or to safeguard or promote his welfare.
(b) For purposes of this section, "in loco parentis" includes grandparent and guardian, any person acting by, through, or under the direction of a court with jurisdiction over the child, and anyone who has express or implied consent of the parent or parents.