I received a note a couple of days ago from a gentleman concerned about the placement of commas in the various drafts of the Second Amendment. And today, at The New Yorker, Jeffrey Toobin writes that "the text of the amendment is divided into two clauses and is, as a whole, ungrammatical." Well, The New Yorker may not be the best place to go for instruction on grammar and usage. The Founders (it's a little vexing to have to keep explaining this) loved Latinate constructions, one of which is the absolute, a phrase modifying a whole clause, often consisting of a noun and a participle. The Second Amendment opens with just such an absolute: "A well regulated militia being necessary to the security of a free state." Modifying the succeeding clause, "the right of the people to keep and bear arms shall not be infringed," it puts the right in the context of the establishment and operation of a militia.*
Commas don't much enter into it. Eighteenth-century writers like to insert a comma between subject and verb, though we don't follow such a convention any longer. The comma in the Second Amendment merely sets off the absolute.
We still have absolute phrases in English, and we typically set them off with commas, viz., The point having been made repeatedly, further discussion would seem idle.
Happily, when Mr. Toobin turns from grammar to the law, he is more persuasive, pointing out that for most of the Republic's history, legal thinking construed the Second Amendment to be about militias rather than an individual right to possess firearms. That understanding, he argues, is a constitutional novelty, developed though political pressure by the National Rifle Association and Supreme Court decisions during the past forty years.
He observes, a little snidely, "Conservatives often embrace 'originalism,' the idea that the meaning of the Constitution was fixed when it was ratified, in 1787. They mock the so-called liberal idea of a 'living' constitution, whose meaning changes with the values of the country at large. But there is no better example of the living Constitution than the conservative re-casting of the Second Amendment in the last few decades of the twentieth century."
*Please, before the more mercurial among you rush to comment, let me repeat that I am not advocating a ban on private ownership of firearms and am not conspiring with the wicked federal government to take yours away.