The Pentagon is developing plans to restructure the National Guard in Washington, D.C., in a move to address problems highlighted by the chaotic response to the Jan. 6 riot and safety breaches during the 2020 protests over the murder of George Floyd, The Associated Press has learned.
They couldn’t deploy until someone gave the order to deploy.
This authority to activate the D.C. National Guard has been delegated, by the President, to the Secretary of Defense and further delegated to the Secretary of the Army. The D.C. National Guard is the only National Guard unit, out of all of the 54 states and territories, which reports only to the President.
Basically Trump and the above listed people didn’t order them to them to be deployed.
So Pence ordered it, which is not strictly legal, but that’s how things had to go with the president attempting a coup.