The United States faces a number of significant national security threats, ranging in scope from intercontinental ballistic missiles to the use of weapons of mass destruction (WMD) by terrorists. The debate over the seriousness of the various threats intensified recently, even before the events of September 11, 2001. Various studies and commissions recommended far reaching changes in the U.S. approach to domestic preparedness and response to threats to the homeland, many now being implemented. Many experts believe the probable long term effects of a WMD attack by terrorists on the population, environment, and the economy make it imperative that the U.S. be fully prepared to either deter or interdict an attempted terrorist attack. This paper reviews the current legislation and policies that govern the military's role when supporting law enforcement in a domestic terrorism crisis and highlights some of the issues confronting the U.S. government. To fully understand the military's role in domestic crisis response it is necessary to explore existing nationallevel structures and response options prior to the involvement of military forces. Crisis management is predominately a law enforcement function that manages the resources necessary to prevent or resolve a terrorist incident, including one involving WMD. Current U.S. government terrorism response policy is contained in presidential directives. Among other matters, these directives address National Security Council structure and federal agency crisis response roles when responding to a domestic terrorism incident. The creation of the Department of Homeland Security and U.S. Northern Command has not yet changed the basic roles and relationships described herein. Many federal agencies are available to assist the Federal Bureau of Investigation (FBI) in dealing with a terrorist threat or in the resolution of an actual terrorist incident. The Department of Defense (DoD), as a supporting agency in domestic law enforcement operations, has developed and maintains plans and capabilities to respond to threats or acts of terrorism, including those involving the use of nuclear, biological, or chemical weapons. In a domestic crisis, DoD may be called upon to assist in several different ways ranging from actual interdiction of the terrorists to the loaning of specialized equipment for use by law enforcement agencies. DoD has published specific policy for assistance to civil law enforcement officials in emergencies involving terrorism and WMD. U.S. terrorism policy is an issue of growing policy debate. Most experts believe that a comprehensive national strategy for domestic terrorism is a critical step in defeating the threat. Some say more effectively employing DoD's capabilities during domestic crisis response operations, or new relationships based on the recent creation of the Department of Homeland Security are the best methods to ensure success against domestic terrorism. Lastly, newly proposed congressional oversight roles are seen by many as an important factor in a more effective response to domestic terrorism. This report will be updated should major changes occur to the relationships described.