So You Think You Know the Second Amendment? - The New Yorker. I have been teaching this to Constitutional Law classes for a dozen years.

"For more than a hundred years, the answer was clear, even if the words of the amendment itself were not. 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.” The courts had found that the first part, the “militia clause,” trumped the second part, the “bear arms” clause. In other words, according to the Supreme Court, and the lower courts as well, the amendment conferred on state militias a right to bear arms—but did not give individuals a right to own or carry a weapon."

So You Think You Know the Second Amendment? - The New Yorker