Indiana Code Title 10. Public Safety § 10-16-7-9

(1) insurrection, rebellion, invasion, tumult, riot, resistance to law or process, breach of the peace, or public disaster, occurs in the vicinity of a station of the Indiana national guard;

(2) the exigencies of a situation make it impossible for the senior commanding officer of the Indiana national guard station to communicate with the governor or the adjutant general;  and

(3) the sheriff of the county involved or an officer acting on behalf of the sheriff provides the senior commanding officer of the Indiana national guard station with a written request signed by the sheriff of the county involved or officer stating the facts and the nature of the service desired;