With approximately 20,000 National Guard in Washington D.C, here is some interesting General Military Law.
To the extent specifically authorized in the designation made by the Secretary of Defense in accordance with Section 2672(b), an officer or agent may exercise one or more of the following powers:
a. Enforce federal laws and regulations for the protection of persons and property.
b. Carry firearms, pursuant to DoD Directive 5210.56.
c. Make arrests:
(1) Without a warrant for any offense against the United States committed in the
presence of the officer or agent; or
(2) For any felony cognizable under the laws of the United States if the officer or agent
has reasonable grounds to believe that the person to be arrested has committed or is committing a felony.
d. Serve warrants and subpoenas issued under the authority of the United States.
e. Conduct investigations, on and off the property in question, of offenses that may have been committed against property under DoD jurisdiction, custody, or control, or persons on such property.
Source: US HOUSE GOV