Jeffrey Toobin, "So you think you know the second amendment?", The New Yorker 12/18/2012:
The text of the amendment is divided into two clauses and is, as a whole, ungrammatical: “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.”
Coming from The New Yorker's house legal analyst, this is shocking.
John McIntyre explains ("Give up on the Second Amendment's grammar", The Baltimore Sun 12/19/2012):
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.
The grammar and punctuation of the second amendment are discussed at greater length in "Once is cool, twice is queer", 11/27/2004, and "The right to keep and bear adjuncts", 12/17/2007. The second post notes that the obvious grammatical analysis of the second amendment is part of the standard legal discussion of its meaning, quoting Nelson Lund, "A Primer on the Constitutional Right to Keep and Bear Arms", (Virginia Institute for Public Policy, 2002):
If you parse the Amendment, it quickly becomes obvious that the first half of the sentence is an absolute phrase (or ablative absolute) that does not modify or limit any word in the main clause. The usual function of absolute phrases is to convey information about the circumstances surrounding the statement in the main clause, such as its cause. For example: "The teacher being ill, class was cancelled."
As Prof. Lund's example indicates, absolute constructions remain part of the grammar of standard written English. Some particular instances remain common enough to be considered cliches: "this being the case", "other things being equal", "all things considered", "that said". It's New-Yorker normal that Jeffrey Toobin is ignorant of elementary grammatical analysis, but it's surprising that his ear for ordinary English usage is so bad, and that he's apparently unaware of the standard legal discussion of the constitutional issue on which he's providing an allegedly expert opinion.
For more on the language of the second amendment, see "What did it mean to 'bear arms' in 1791?", 6/18/2008.
Update — Note that Toobin's citation of the text omits two commas that are present in the official transcript of the 2nd amendment:
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.
These commas are discussed at length in one of the posts linked above, which observes that commas between subject and predicate were common in the 18th century, though they are outside the norms of contemporary standard punctuation. Since Toobin doesn't mention them, and omits them from his citation, we can assume that the commas are not the locus of his reason for concluding that the amendment "is, as a whole, ungrammatical".
So why DOES Toobin think that the amendment "is, on the whole, ungrammatical"? He doesn't say. I assume that he believes that absolute constructions are Not Allowed — presumably by a vague analogy to "dangling modifiers", though the two constructions are clearly different.
Update #2 — Eugene Volokh, "The Commonplace Second Amendment", 73 NYU L. Rev. 793 (1998), observes that "Many contemporaneous state constitutional provisions are structured similarly". He means that they contain "a statement of purpose" preparatory to stating a right or other point of law.
In many of his examples, the "statement of purpose" is a separate tensed clause, e.g. "The Liberty of the Press is essential to the security of freedom in a state; it ought, therefore, to be inviolably preserved", or "The freedom of deliberation, speech, and debate, in either house of the legislature, is so essential to the rights of the people, that it cannot be the foundation of any accusation or prosecution, action or complaint". But he cites other cases where the "statement of purpose" is expressed as a NP+ParticipialPhrase adjunct,e .g. "The liberty of the press being essential to the security of freedom in a state, any person may publish his sentiments on any subject, being responsible for the abuse of that liberty…", or " Economy being a most essential virtue in all states, especially in a young one; no pension shall be granted, but in consideration of actual services…"
There are quite a few currently-common idioms with the same (NP+Participle) structure, e.g. "That being said", or "Other things being equal" — these are common even in the pages of the New Yorker.
(link) That being said, someone recently told me that I could have written a story about killing babies and it would probably offend fewer people.
(link) A law degree is probably a helpful credential, all other things being equal, for a trial judge or an appeals-court judge.
And less cliched examples also occur, though perhaps not as commonly today as in the 18th century. The searching features of the COCA interface make it easy to find examples:
From The Atlantic: This being Silicon Valley, however, Obama was quickly embraced.
From Art Bulletin: The prints having been acquired, she then wanted him to have the famous antiquarian Ridolfino Venuti arrange them…
From Skiing magazine: A beer being a terrible thing to waste, I spent a good 45 minutes with one right then and there.
From the Raritan Review: A badgeless MLA being inconceivable (since much of the representational foundation would then collapse, and even drifting would become impossible since there would be no structure from which such an activity could veer), I had to get a badge in order to fit in.
From the Smithsonian magazine: No world-championship event being scheduled this year, this smaller get-together provided a good glimpse of what harmonica people are like, and what they like to do.
From the Christian Science Monitor: Our lesson having been learned back at the hotel, we slipped him $3 and asked him to try harder.