The easiest way to illustrate state troops is equate them to today's National Guard. Each state maintains an army and an air force which is under the command of the Govenor through his adjutant general. Under U.S Code Title 10, the POTUS is authorized to federalize the National Guard for a specific duty for a specified time. As an illustration I will give my Katrina story. As a member of the Miss Air National Guard 172nd Medical Group, we were called to duty by Haley Barbour, Govenor. All National Guard troops who responded to the coast at that early stage were responsible only to their soverign state or turned over to the state of Mississippi. It was only about a week later that we all became federalized under Title 10 and called to active duty retroactive to the date of the disaster. Prior to that the active duty military (Tite 10) regulars had no command and control over any national guard unit and once federalized the command structure in place was essentially unchanged, the respective commanders, i.e. the ADjuntant General of Mississippi became the ranking officer and in command of all operations within Mississippi. The active duty guys did whatever it was they did and the National Guard toted the load.