More to the point, “regulated” at the time and in this particular context meant “trained and drilled” by a professional soldier (usually the equivalent of an NCO). For example, the original 1778 U.S. army field manual, von Steuben’s “blue book”, was titled “The Regulations for the Order and Discipline of the Troops of the United States”. The term was basically shorthand for “by-the-book training”.
The Framers didn’t envision a bunch of amateur yahoos taking potshots with muskets winning a war against a foreign oppressor. They knew from their own recent experience that guerilla warfare had its limits against a global military power like Britain, and that discipline and organisation and regular training were the only ways an American militia could prevail in battle.
That one term is more evidence that the original primary intent of 2nd Amendment was more about establishing citizen militias like today’s National Guard – certainly more than it was about letting insecure fantasists fondle their collections of masculinity totems.
[ETA: this is the core irony of Scalia being regarded as the great “originalist” in re: Heller]
