Posse Comitatus Act
The Posse Comitatus Act is a United States federal law that was enacted in 1878 after the end of Reconstruction. It prohibited originally the federal troops to supervise elections in the former Confederate states. Even today it is the military Posse Comitatus Act because of the impossible, such as the police to enforce law and order - unless the Constitution or the Congress allow exceptions.
The original law of 1878 concerned only the army of the United States, the U.S. Army. The Air Force was added to the Act in 1956, and the U.S. Navy and the U.S. Marine Corps were asked by a decree of the Ministry of Defence under the Posse Comitatus also law.
Excluded from these provisions is the National Guard, if they are under the command of the governor. Also, there are exceptions for the Coast Guard and other troops, such as the Joint Interagency Task Force ( Naval Air Station, Key West, Florida), which deals with the suppression of drug trafficking.
As a result of social unrest in New Orleans and other expected social unrest and protests of more and more affected by casualization citizens there is tendencies to legalize the use of the army against the population.