JP 3-28, page 16

Executive Summary xiv JP 3-28 Command and Control in United States Northern Command and United States Pacific Command Areas of Responsibility For DSCA operations, SecDef designates a supported combatant commander. Ordinarily, this will be Commander, US Northern Command, for the continental US, Alaska, Puerto Rico, and the US Virgin Islands and Commander, US Pacific Command, for Hawaii, Guam, American Samoa, and the Northern Mariana Islands. The Chairman of the Joint Chiefs of Staff (CJCS) may publish, if required, a SecDef-approved execute order (EXORD) to further delineate support relationships, available forces, end state, purpose, and SecDef-approved scope of actions. Planning Considerations for Defense Support of Civil Authorities To expedite planning and operational response during crisis situations, the CJCS publishes a DSCA EXORD and a chemical, biological, radiological, and nuclear response EXORD to allow prompt force deployment in support of domestic incidents. DOD planners work hand-in-hand with NG and civilian planners to develop tailored regional civil-military plans for DSCA. These plans inform local, territorial, tribal, state, and national planning efforts. Supporting Civilian Law Enforcement Agencies When requested, federal forces may provide support to federal, state, territory, tribal, insular areas, and local law enforcement organizations reacting to civil disturbances, conducting border security and counterdrug missions, preparing for antiterrorism operations, and participating in other related law enforcement activities. The requested support must be consistent with the limits Congress placed on military support to law enforcement through the Posse Comitatus Act (PCA) and other laws. The Posse Comitatus Act The primary restriction on DOD participation in civilian law enforcement activities is the PCA. IAW DOD policy, unless specifically authorized by law, no DOD personnel in a Title 10, USC, status will become involved in direct civilian law enforcement activities, including, but not limited to, search, seizure, arrest, apprehension, stop and frisk, surveillance, pursuit, interrogation, investigation, evidence collection, security functions, traffic or crowd control, or similar activities, except in cases and under circumstances expressly authorized by the President, Constitution, or act of Congress.