logic behind closing it is probably that the DoD doesn't want to pay the staff to work overnight hours. i doubt they'd let anyone in there unsupervised to cover their asses in the event of a lawsuit.
and quantico is not exactly a closed community; it's a small base so housing is just incorporated with everything else, and any civilian can get on this base just by showing a driver's license. they compensate for this by having you show military ID in order to use pretty much anything on base from medical facilities to the gym to making purchases at any store.
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