On October 17, 2006, President Bush signed into law, the John Warner Defense Authorization Act. The law allows the President to declare a “public emergency” at his own discretion, and place federal troops anywhere throughout the United States. Under this law, the President also now has the authority to federalize National Guard troops without the consent of Governors, in order to restore “public order.” The President can now deploy federal troops to U.S. cities, at will, which eliminates the 1878 Posse Comitatus Act.
This means the president holding office will control everything, including the arrest of whomever he deems threatening. All communications are controlled, all media is controlled and now the president controls DHS, the military and police.
All the joint training we are seeing between the military and police leading up to Jade Helm, it's a qualification, the police and sheriff departments are being qualified for federalization. Personnel have to be qualified first, before they can participate in joint operations (signed off). This is how the system works.
Also, the other reason for this is for tracking and supply. The government uses specific forms that are entered into the logistics and supply system. If everyone is federalized, the system runs smoothly, because everyone is government document/program number approved and recognized by the same system, not an off shoot agency that require more work to track and less benefits when supplying personnel and units.