Here is a remarkable development. Just twenty-five years ago, there was a strong consensus, among judges and academics, that the Second Amendment did not create an individual right. No federal court had invalidated a restriction on guns on Second Amendment grounds (ever). As recently as 1992, Chief Justice Warren Burger, a conservative Republican appointee, rejected the individual rights view in public. (For some details, see my TNR piece, "The Most Mysterious Right.")

In a short period, the consensus has shattered. There is a strong possibility that the Supreme Court will accept a view that seemed utterly implausible in the relatively recent past. Here is the question: What has happened?

Consider four possibilities:

1) Truth has finally prevailed. Perhaps new research has shown that the individual rights view is correct. It is true that a large amount of work has been produced in support of that view. Much of it has been funded by private groups with a stake in the issue--but hardly all of it.

2) Interest groups, above all the National Rifle Association, have spurred the change. Perhaps the new view is a reflection of an aggressive social movement, not unlike the movement to ban segregation and to create a right to same-sex marriage. There can be no doubt that a great deal of time, money, and effort have been expended in an effort, by those with a serious stake, to press the individual rights view on politicians and the federal courts.

3) Both politics and law have experienced an informational cascade, produced by determined and savvy "Second Amendment entrepreneurs." Many of those involved in law and politics do not have a lot of private knowledge about the Second Amendment. They must rely on what others think. When others seem to think that the individual rights argument is right, they defer--at least if they trust those others. On this view, the apparently supportive views of "liberal academics"--including Sanford Levinson, Akhil Amar, Lawrence Tribe--have been crucial in legitimating the individual rights position.

4) New judicial appointees have shown new receptivity to arguments that are a) originalist and b) associated with the political right. A key contributor to the shift is undoubtedly the presence, on the federal bench, of a number of Reagan and Bush appointees, who are sympathetic to gun rights in particular, and who also have a jurisprudential interest in originalist arguments.

I tend to think that all of these explanations provide part of the picture, with the (important) qualification that 1) is probably wrong. (This is not the place to defend the qualification. The original understanding of the text is very complex, as shown by historians Saul Cornell and Jack Rakove among others; and longstanding social practices and many court of appeals have refused to accept the individual rights interpretation. In my view, the individual rights view, at least in its present form, is mostly a product of contemporary concerns and preoccupations. For some details, see my article.) Even if is right, it is not an adequate explanation of what has happened.

If we put 2), 3), and 4) together, we will see that the individual rights interpretation has been the beneficiary, above all, of a stunningly successful social movement. In the domain of constitutional law, there has been nothing even vaguely like it in the past quarter-century--and it isn't easy to think of a close parallel, ever.

--Cass Sunstein