A well regulated Militia, being necessary to the security of a free State, the right of the people to keep and bear Arms, shall not be infringed.
Everything up to “State” is a preamble, a statement of fact (or apparent fact) that justifies the statement of the right that follows. (It’s probably best to ignore the first and third commas: people used a lot more of them back then.)
This needs a bit of unpacking. The argument implicit in the Second Amendment is this:
(a) We want the state to be secure.
(b) A well-regulated militia is necessary to the security of a free state.
(c) The right of the people to keep and bear arms is necessary for there to be a well-regulated militia.
(d) The right of the people to keep and bear arms shall not be infringed.
(a) is unstated, but as a general principle it’s completely uncontroversial. (b) is stated, albeit in the form of an absolute clause. (c) is unstated, but is the essential logical link that joins (a) and (b) to (d). And (d) is stated as the main clause of the sentence.
There are two obvious problems with this: (b) is not true and (c) is not true.
First, (b). There are plenty of free states that manage to be secure without having a militia (something distinct from the regular armed forces). It is also hard to argue that what remains of the US militia really makes that essential difference to national security.
Second, (c). It is perfectly possible to have a militia without the general population having the right to keep and bear arms. Local militia organisers could very easily look after the weapons and distribute them at the first sign of the invading English. Also, given that not all citizens would be in a militia, any right to arms need not extend beyond militia members.
Therefore (d) is not justified: the need for the people to have the right to keep and bear arms does not follow from a platitude and two historically short-sighted falsehoods.
And yet there it is, in the Constitution, in black and white.
And so I come back to the oddity of the Second Amendment: uniquely, it doesn’t just state a right but also gives a reason for that right. But it doesn’t therefore follow that the right legally depends on the stated reason.
My objections above are factual and logical. They are not legal objections. I don’t see that my argument justifies an interpretation of the Second Amendment that lets only members of well-regulated militias have access to guns.
What I do see is that this tragic piece of law, which seemed reasonable in 1789 but is now so drenched in the blood of innocents that its existence is an ongoing threat to the security of a free state, should be repealed.