It is currently frowned upon to deploy the National Guard without the governor's direct orders (or in the case of DC the president's direct orders), but they used to deploy themselves in emergencies, and not wait the days it used to take to contact the governor. For instance, if a fugitive was on the run, there was no police force, so the militia would just deploy.
So it is sort of OK for the National Guard to deploy in a law enforcement manner until actually ordered to not by the governor (or in this case president).
It was an ugly situation, and trump may well have uglier situations in store for us.