The conditions include military support needed “to prevent significant loss of life or wanton destruction of property and are necessary to restore governmental function and public order.” A second use is when federal, state and local authorities “are unable or decline to provide adequate protection for federal property or federal governmental functions.”
Inside the Ring: Directive outlines Obamas plan to use the military against citizens - Washington Times
"“In these circumstances, those federal military commanders have the authority, in extraordinary emergency circumstances where prior authorization by the president is impossible and duly constituted local authorities are unable to control the situation, to engage temporarily in activities that are necessary to quell large-scale, unexpected civil disturbances” under two conditions.
