"...the majority of DOD support is coordinated using the concept of DSCA. However, imminently serious conditions resulting from any civil emergency may require immediate action to save lives, prevent human suffering or mitigate property damage. When such conditions exist, and time does not permit approval from higher headquarters, local military commanders and responsible officials from DOD components and agencies are authorized to take necessary action to respond to requests from civil authorities. This response must be consistent with the Posse Comitatus Act, which generally prohibits Federal military personnel (and units of the National Guard when they are acting under Federal authority) from acting in a law enforcement capacity (e.g., search, seizures, arrests) within the United States, except where expressly authorized by the Constitution or Congress". (DHS, National Response Framework -- Federal Partner Guide (Comment Draft), September 10, 2007, p. 20)