Defense support of civil authorities (DSCA) is support provided by federal military forces, Department of Defense (DOD) civilians, DOD contract personnel, DOD component assets, and National Guard (NG) forces (when the Secretary of Defense SecDef], in coordination with the governors of the affected states, elects and requests to use those forces in Title 32, United States Code, status or when federalized) in response to requests for assistance from civil authorities for domestic emergencies, law enforcement support, and other domestic activities, or from qualifying entities for special events. DSCA in the US presents a unique challenge based on the history of the country and the interaction of the federal, state, local, territorial, and tribal governments and private and nonprofit organizations. These relationships establish the multiple layers and mutually reinforcing structures throughout the state and territorial governments for interaction based on the US Constitution, as well as on common law and traditional relationships.