In some cases, Guard members are “deputized” and given limited law enforcement authority.
My unit was mobilized as part of the Inaugural security in 2009, and we were all “sworn” and deputized for a 72-hour period
In some cases, Guard members are “deputized” and given limited law enforcement authority.
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There would have to be a law enforcement entity to do the deputizing. Since your example was a Federal mission, perhaps the U.S. Marshalls did the deputizing. With regard to the Virginia state brouhaha, I know the President would never approve any LE entity in the Executive Branch to deputize the Guard.