In a way, it doesn't. There's really no way to arm yourself in a fashion to survive sustained attack from the U.S. military in this day and age.

But that's one of the reasons the military are sworn to uphold and defend the Constitution as the primary goal, not simply to obey orders. They even throw in the surreal weasel words "against all enemies, foreign and domestic" as a way of really punching that point home.

So it's not really possible to meet the full intent of the 2nd Amendment any longer but at the same time there are other safeguards.