The Insurrection Act is a federal law that empowers the president to deploy the military to suppress certain situations including civil disorder, insurrection, or rebellion.
The act has been used to send the armed forces to quell civil disturbances a number of times during U.S. history, according to the Congressional Research Service. It was most recently invoked during the 1992 Los Angeles riots after four white police officers were acquitted in the roadside beating of a Black man, Rodney King, and during Hurricane Hugo in 1989, when widespread looting was reported in St. Croix, in the U.S. Virgin Islands.
The Insurrection Act is a federal law that empowers the president to deploy the military and federalize National Guard troops to suppress certain situations including civil disorder, insurrection, or rebellion.
Martial law, by contrast, is a concept that doesn’t have a legal definition in the U.S. At its most extreme, it reflects the suspension of civil authority and military control of civilian functions such as the courts
In 1866, the Supreme Court ruled that martial law cannot be imposed where civil courts are open and functioning. Martial law as a state of affairs arising from a total breakdown of civil order.