Are law and politics separate realms? That’s the ideal. But Adam Liptak, Supreme Court reporter for The New York Times, raises questions today about whether it’s any longer the case. Drawing on a study published last month in The Vanderbilt Law Review and summarized in the autumn issue of The Green Bag, which collected data from 1882 through 2006, he notes that, beginning around 1990, Supreme Court clerks “started to take jobs that reflect the ideologies of the justices for whom they worked.” That’s “cause for concern,” says one of the study’s authors, NYU law professor William E. Nelson, “because it’s a further piece of evidence of the polarization of the court.”

In particular:

Clerks from conservative chambers are now less likely to teach. If they do, they are more likely to join the faculties of conservative and religious law schools. Republican administrations are now much more likely to hire clerks from conservative chambers, and Democratic administrations from liberal ones….

The Clinton administration hired 96 former clerks, but only 16 percent of them came from the chambers of the four most conservative justices…. Of the 89 former clerks hired by the administration of George W. Bush, on the other hand, 68 percent came from those four chambers.

More striking still is what the study shows about the legal academy. From about 1940 to 1990, “about a third of all clerks became law professors,” with little correlation to the justices ideological leanings. (N.B.: “conservative” justices were few and far between until late in that stretch.) But more recently “only 19 percent of clerks from the four most conservative justices … joined the legal academy and only 7 percent went to one of the top 10 law schools” as ranked by U.S. News & World Report. And “a significant minority joined the faculties of religious or conservative law schools.” (“Conservative law schools,” I should note, may be close to an oxymoron.) By contrast, “clerks for the other five justices followed the historical pattern, with 34 percent joining the legal academy, about half of them at the elite schools.”

All of which, the study says, reinforces the idea that the court is “a superlegislature responding to ideological arguments rather than a legal institution responding to concerns grounded in the rule of law.” And that, Liptak concludes, “is not easy to reconcile with the view that that law and politics are, or at least ought to be, different realms.”

It’s good to have all of this drawn together, but it’s hardly surprising to anyone who’s been watching the law schools, the courts, and the law over the years. Liptak points to an important source of this change: “The rise of the organized conservative legal movement, including notably the Federalist Society,” which resulted in turn from “the sense among conservatives that law school faculties are overwhelmingly liberal.”

It’s no accident, therefore, that the change became noticeable around 1990. The Federalist Society came into being only in 1982. Over the next several years it would slowly influence the legal debate — in the law schools, and later among lawyer practice groups — and influence future clerks along the way. And it was only during the Reagan administration that Republicans began to approach nominations to the Court more seriously and systematically, from an ideological perspective.

But those efforts were not the root cause of today’s politicization of the courts and the law. They came about because the law schools, the courts, and the law were already long politicized – albeit in only one direction, which gave a deceptive picture. When all three institutions were marching only one way, toward the modern administrative state, it seemed that there was little dissension, and hence little politicization. But in truth, the politicization of the law — politics replacing law — had begun much earlier, with the Progressives; it was institutionalized by the New Deal Court; and it continued until the late 1960s and into the 1970s, when conservative and libertarian legal scholars began to call for separating politics and law. See here for a more detailed treatment of those developments, and here for the roots of our politicized law in the Progressive Era.