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Because there's a suspension of civil liberties within X miles of a border, and the power can be exercised by the USBP.

(Edit: see map posted in a sibling comment. See position of Minneapolis on said map)

Here’s a map of their jurisdiction:

Probably because US border patrol has aerial surveillance vehicles and lots of experience in their use, and the national guard likely does not

They both have experience, US National Guard would require DoD approval to fly domestic missions.