Pres Trump is the Commander in Chief in charge of the National Guard in D.C.

https://wamu.org/story/21/01/11/dc-national-guard-deployment-capitol-delay/

What exactly is the National Guard?

The National Guard is the U.S. military’s domestic force. Each state, the District and Puerto Rico have their own National Guard units. Troops have occasionally been called upon to serve overseas, as they were in Iraq and Afghanistan after the Sept. 11 attacks. But their main mission is at home. The largest such effort was to help the Gulf states after Hurricane Katrina in 2005.

Members traditionally serve one weekend a month — unless called upon by their state, local or federal government for emergency assistance. More than 2,700 soldiers and airmen make up the District of Columbia’s National Guard.

Who’s responsible for deploying them locally?

Typically, the governor has the authority to activate guard troops within a state’s borders. He or she informs the adjunct general to mobilize troops. The adjunct general sends the message down the chain of command.

It’s more complicated in D.C., as are most things around here.

Mayor Muriel Bowser does not have the same authority over the D.C. National Guard that governors have over their states. She can only request guard troops from the Secretary of the Army. That request then gets sent up the chain of command to the Secretary of Defense for approval.

[Incumbent Christopher C. Miller Acting since November 9, 2020 was appointed by Pres Trump]

Even then, Bowser’s jurisdiction is limited. Because of the District’s finicky federal status of not being a state, she can only request guard troops to land that belongs to the city. That excludes federal territory, like the Capitol and its environs. The Secretary of Defense needs to approve the deployment of National Guard troops from any jurisdiction at federal land like the Capitol complex.

What’s the process for sending guard troops here from elsewhere?

When the District needs additional troops from other states, those states’ governors must receive an invitation from high-level officials at the Pentagon. In cases like natural disasters, states have emergency agreements between them to send guard troops as quickly as possible.

Once a state’s guard unit is mobilized to go into another jurisdiction, there’s a lag time. It can take anywhere from 8 to 10 hours for the unit to arrive.