So, questions for discussion, directed at former military folks

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11. They are likely there for security only

In my experience they are there to protect and defend the Capital in support of civil authorities. Law enforcement (dissipate the crowd) is normally left to civilian law enforcement while the NG supports; normally the NG is placed in a role where they are NOT required to enforce civilian laws. Cordons and traffic control are good examples. In this scenario it appears they are part of the perimeter and internal security, which is likely a means of preventing a breach.

Laws governing military forces (USC Title 10 and Title 32) are very restrictive when using military personnel for law enforcement.