The principal is empowered to take appropriate action against non-students who infringe upon any school grounds or property
Such action includes the right to call in the police and swear out warrants.
The authority for such is Article 5, 166-551 of the South Carolina Code of Laws Disturbing Schools -
It shall be unlawful: (1) for any person willfully or unnecessarily (a) to interfere with or disturb in any way or in any place the students or teachers of any school or college in this state, (b) to loiter around such school or college premises, except on business, without permission of the principal.
Any person violating any of the provisions of this section may incur a fine.