Martial law occurs when the military assumes police powers because local authorities and courts aren't functioning. Although the president usually imposes martial law, federal regulation allows for a "local commander" to do so "on the spot, if the cir stances demand immediate action."
Federal armed forces are expected to relinquish these powers as soon as the local government is once again operable. During martial law, the military may arrest and try civilians, seize private property, and ins ute curfews, among other emergency powers.