NoBoxes

Those citizens would have to deploy some pretty heavy armament before that notion became a serious consideration. The government generally isn't worried about a citizenry with small arms overthrowing it. The city isn't worried about even it's armed police force overthrowing it; because, it can go to the State for National Guard support. The State isn't worried about it's armed National Guard overthrowing it; because, it can go to the Federal Government for Armed Forces support. The Federal Government isn't worried about the Armed Forces overthrowing it; because, there is a citizenry with small arms that could deny a total victory to the Armed Forces as it's experiencing in Iraq and Afghanistan. Subversive citizens would need to use much more force to install a different government than the general population would need to prevent the government, if the government slips, from installing all different citizens.

Additionally, subversive citizens can pose as much danger (via domestic terrorism) to non-government personnel as to government personnel. Would you take away the non-subversive general population's ability to defend themselves with small arms? The subversives are going to acquire small arms whether they can be legally owned or not. The government can't even keep illegal drugs or illegal aliens out of this country let alone firearms.