Hmmm. I don't think I would have the slightest problem with our gubmint taking assault rifles, machine guns, RPG's and the like out of US citizens' hands if those in possession are unable to prove ownership or show proper licenses.
US Troops, disarming Americans?
Perish the thought. Aside from it being a violation of US Code, Title 10, The Posse Comitatus Act of 1807 precludes it.
It's a matter of perspective.... Example: A US Soldier on a Baghdad street, kicking down doors and confiscating weapons is a Hero, doing a distasteful and dangerous job, deemed critical by his lawful commanders.
That same troop, armed and under the same orders in
my town would be, by legal default; acting unlawfully. If he made the attempt of home invasion and disarming me and I resisted by force that attempt, then I would be legally protecting my person, family and property.
Since it's likely neither of us would survive to sit in judgment by our peers; it'd be up to prosperity to decide who was right.