Contingent Military Operations
Section 215 which provides the basis for executive power in this area, provides a contingency plan for martial law including plans for troop deployment, control of the populace, and control of information passing between civilians and the government.
These contingency procedures delegate to the Secretary of the Army most of the authority given to the President by chapter fifteen. Section 215 authorizes the Secretary of the Army and politically appointed subordinates to call federal reserve units and state National Guard units into active service. The Secretary coordinates the mobilization with all local civil and military authorities and directs deployment of military resources through military commanders. A civil disturbance need not be present to deploy troops; it is sufficient that there is a potential for a disturbance.
The contingency plans are consistent with the present military policy known as the Army Doctrine. Under the Army Doctrine, the military would retain control of troops in the area subjected to martial law and take command of the local government. Total or partial control of troops by civil officials in the true historical sense of a posse comitatus is usually avoided. Although the military has established military tribunals only in grave situations, such as in the midst of actual warfare, this limitation is maintained only in older cases such as Ex parte Milligan. Training procedures for establishing military tribunals are maintained but will not, according to the Doctrine, be implemented unless civil courts are closed. The military, however, may close the courts as they did in 1941 when martial law was established in Hawaii after the bombing of Pearl Harbor.
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By claiming the right to use the military in national disasters and calamities, the executive can utilize the contingency plans of the Office of Emergency Preparedness. These plans provide for control of elements within a geographic area. Deploying troops means that the Joint Chiefs of Staff and their military subordinates assume command over the locale, displacing state and local officials. The planning information for controlling the populace is unavailable to the public. It is available, however, to the various commanders at the time troops are mobilized. All information released to the public is controlled ,by the Assistant Secretary of Defense. In certain instances the military may even take control of the news media in the area, particularly the broadcasting industry, and disseminate the news.
https://core.ac.uk/download/pdf/188096313.pdf