First, who could order it?
It goes from the Secretary of the (Service) to the Secretary of Defense to the President, however, in a unique arrangement, the DC National Guard is commanded directly by the President as is emphasized in the following by the words “at all times”. Note also no chain of command to any higher military units for any of the services.
***From Wiki: “The President of the United States is the Commander in Chief of the National Guard of the District of Columbia at all times. Command is exercised through the Secretary of Defense and the Commanding General, Joint Force Headquarters, District of Columbia National Guard. The Secretary of Defense has delegated his command authority to the Secretary of the Army for the District of Columbia Army National Guard and the Secretary of the Air Force for the District of Columbia Air National Guard. The District of Columbia National Guard is commanded by a Major General with a Brigadier General as his or her adjutant. The Mayor of the District of Columbia, or the United States Marshal for the District of Columbia, or the National Capital Service Director, may request the Commander in Chief to aid them in suppressing insurrection and enforcement of the law.”***
Donald Trump officially becomes president at noon and this change of general occurs at 12:01. “...Inauguration Day takes place on January 20 following a presidential election. The term of a president commences at noon (ET) on that day, when the Chief Justice administers the oath to the president.”
Obama is no longer calling the shots at that point.
So, for some reason Trump is doing this. The new secdef or secservice(s) won’t be in place by next Friday. Ash Carter will still be the SecDef and his service secretaries the SecArmy/Navy/AF/Marines/CG.
Sounds like Trump has an issue with the guy.
"Normally, American federal law specifically charges the U.S. National Guard with dual federal and state missions. As the U.S. federal government abolished the jurisdiction of the state of Maryland and states rights in Washington, D.C. to establish a federal district, there is no elected governor to command this guard unit. This is the only national guard unit that reports only to the U.S. president.
The U.S. National Guard is the only United States military force empowered to function in a state or, in this case, a district status. Those functions range from limited actions during non-emergency situations to full scale law enforcement of martial law when local law enforcement officials can no longer maintain civil control. The National Guard may be called into federal service in response to a call by the President or Congress."
https://en.wikipedia.org/wiki/District_of_Columbia_National_Guard