Recognizing the risk that a standing army could pose to individual civil liberties and the sovereignty retained by the several states, but also cognizant of the need to provide for the defense of the nation against foreign and domestic threats, the framers of the Constitution incorporated a system of checks and balances to divide the control of the military between the President and Congress and to share the control of the militia with the states. This report summarizes the constitutional and statutory authorities and limitations relevant to the employment of the armed forces to provide disaster relief and law enforcement assistance. The Posse Comitatus Act (PCA), 18 U.S.C. In the event of a disaster that results in the wide-scale deterioration of civil law and order, the authority to employ active duty troops to perform law enforcement functions must be found elsewhere. The Stafford Act does not authorize the use of federal military forces to maintain law and order. If the state's National Guard units are called into federal service to respond to an emergency or a major disaster, their role is restricted to the disaster relief operations authorized under the Stafford Act.
Natural disasters, such as Hurricane Sandy, raise questions concerning the President's legal authority to send active duty military forces into a disaster area and the permissible functions the military can perform to protect life and property and maintain order. The Stafford Act authorizes the use of the military for disaster relief operations at the request of the state governor, but it does not authorize the use of the military to perform law enforcement functions, which is ordinarily prohibited by the Posse Comitatus Act. However, the President may invoke other authorities to use federal troops to aid in the execution of the law, including the Insurrection Act. This report summarizes the possible constitutional and statutory authorities and constraints relevant to the use of armed forces, including National Guard units in federal service, to provide assistance to states when a natural disaster impedes the operation of state and local police.