(a) Subject to Subsection (b), a person permitted to carry a firearm on the campus of a school district may not perform the routine law enforcement duties of a peace officer, including making arrests, unless the duty is performed in response to an emergency that poses a threat of death or serious bodily injury to a student, school district employee, or other individual at the district campus.
(b) Subsection (a) does not apply to a commissioned peace officer who is assigned law enforcement duties that are included in campus and district documents describing the role of peace officers in the district as required by § 37.081(d).