Well, I think what 'arms' they were talking about does matter. Should a person be allowed to own a nuclear weapon? It has no bearing whatsoever on a militia, does it, and it poses a serious threat: someday the technology for such WMDs may be so trivial that even a lone crazy person would be able to easily recreate it. If we do not restrict such 'arms', at that point society is doomed.
I think it is safe to say that such 'arms' were nowhere within the imagination of the people who ratified the 2nd amendment. So in translating what they were trying to say to modern technology, it helps to look at the purpose of the 2a in the first place: to allow the people the weapons needed to fight a war against tyranny, either from abroad or from home. The line has to be drawn somewhere, and I think the most logical place is at 'weapons suitable for normal infantry troop use', though I would be willing to entertain an alternate 'anything designed for combat other than WMD' theory as well.
What was the most powerful weapon available to the colonists at the time of the American Revolution?
The Cannon was the weapon of mass destruction of the late 1700s. The militia had in fact buried a cannon at Concord specifically to resist the British troops.
Thus by absolutely logical extension, the well-regulated militias should have Strykers with a M68A1E4 105 mm cannon, M2 or MK240 HMG or MMG respectively and MK19 40mm launchers. The well-regulated militias should also have M1A1 or M1A2 Abrams Main Battle Tanks and M2/M3 Bradley Tracked Armored Fighting Vehicles. All of the variants of the HMMWV (including ones with TOW missiles) are necessary to the security of a free state as well.
In fact, the only thing Congress has specific rights to that the states do not is the power to manage the Navy
Why did our founding fathers choose to have the Navy seperate from the states? Because it was capable of projecting power abroad and it was capable of fighting wars abroad. Since only Congress has the power to declare war, it makes sense that Congress would control the means of projecting power to foreign countries.
Thus, by logical extension, the long range capabilities of the Air Force (especially long range bombers and air to air refueling tankers) are something I believe Congress should control. However, I believe fighter jets and short range aircraft, such as helicopters, are definitely within the militias rights to control as they only protect local areas and do not project armed might abroad in terms of foreign conflict. (At least not without the aid of aircraft carriers or air to air refueling tankers, which would both be controlled by Congress.) Long range nuclear weapons, such as ICBMs should logically be controlled by Congress.
To make a long story short, a standing army is unconstitutional and all of the weapons employed by the US Army should fall under the control of each individual states well-regulated militias. Furthermore, the right of the PEOPLE to keep and bear such arms should not be infringed.
Yes, I'm making a case for private ownership of M203 40mm grenade launchers. Yes, I'm making a case for private ownership of RPGs, Mah-Deuce, M240s in turrets on top of vehicles, etc. It's constitutional.