It depends on the situation and the relationship. If the non-parent is a step parent, then the law generally permits reasonable discipline if the spouse also permits it. If the non-parent is a teacher or school administrator, then some schools do have this as a potential type of punishment.  As long as they follow their procedures, they can legally use this punishment.If the non-parent is stranger, or mostly unknown character, then the non-parent has absolutely no authority to touch another person's child with a belt.Many schools and step-parents wisely shy away from using belts to punish children that are not theirs.  The law permits a reasonable amount of discipline, however, what is reasonable varies by child and parent.  If marks were left on the child, the non-parent could face basic assault charges for striking a child that was not theirs.  If you have a child that has been struck by a non-parent, advise them they do not have your authority to do this again in the future.  If your child has been injured, then notify law enforcement.  If the non-parent continues to engage in aggressive striking, you may have to consider court action to limit the non-parent's access to the child.