(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 Section 37.081(d).