(1/5) The role of the National Guard in response to riots like we saw yesterday is not well understood, so let me try to explain. Guardsmen can be activated under three different statuses:
-State Active Duty (under state control)

(2/5)
-Title 32 Full Time National Guard Duty (under state control but federally funded and in some situations under a different operational chain of command)
-Title 10 Active Duty (also known as 'federalizing' the Guard, under the control of the president)

(3/5) Last night, DOD mobilized up to 6,200 Guardsmen under Title 32. This means they will still technically be under control of the governors, but while in DC they are the operational command of the DC National Guard commander, who answers to the Pentagon & ultimately POTUS.

(4/5) Why not federalize the Guard in this case? The reason is that under Title 10, active-duty military are subject to Posse Comitatus, which prevents them from interacting with civilians (the exception is if POTUS invokes the Insurrection Act, which has not happened)