I believe DC has National Guard.
I’ve been retired for a while, but they used to have Military Police units.
Yes DC has National Guard
Possibly they will be involved in support
I assume the feds have designated a detainment area to process large numbers of detainees
“...but they used to have Military Police units.”
I served 1969-1971 in 519th MP Battalion at Ft. Meade. Our primary mission was riot control, specifically physical security for the White House. Twice a year we did training for the FBI Academy at Ft Belvoir.