Two years ago, Ring v. Arizona (in which Justice Scalia concurred) held that the Jury Trial Clause requires juries, not judges, to find the basic facts underlying the aggravating factors that cause the imposition of a death sentence. But what to do about people who had already been sentenced under the old scheme, and whose sentences were now being reviewed via habeas corpus?

The standard doctrine generally says that new constitutional rules aren't retroactive as to habeas cases, unless the new rule is needed to make the judicial process substantially more accurate. So does the Ring jury trial requirement qualify? In Schriro v. Summerlin, which was decided a few weeks ago, Justice Scalia (writing for the five conservatives) held that it doesn't — and here's the core of his argument:

The question here is not, however, whether the Framers believed that juries are more accurate factfinders than judges (perhaps so — they certainly thought juries were more independent). Nor is the question whether juries actually are more accurate factfinders than judges (again, perhaps so). Rather, the question is whether judicial factfinding so "seriously diminishe[s]" accuracy that there is an "'impermissibly large risk'" of punishing conduct the law does not reach. The evidence is simply too equivocal to support that conclusion.

First, for every argument why juries are more accurate factfinders, there is another why they are less accurate. . . . Members of this Court have opined that judicial sentencing may yield more consistent results because of judges' greater experience. Finally, the mixed reception that the right to jury trial has been given in other countries, though irrelevant to the meaning and continued existence of that right under our Constitution, surely makes it implausible that judicial factfinding so "seriously diminishe[s]" accuracy as to produce an "'impermissibly large risk'" of injustice. When so many presumably reasonable minds continue to disagree over whether juries are better factfinders at all, we cannot confidently say that judicial factfinding seriously diminishes accuracy.

This is a sensible argument, and the distinction Justice Scalia draws with regard to foreign practices — not relevant to the meaning of the right, which should be decided with reference to the Framers' views and American traditions, but relevant to empirical questions, such as those that the Court's retroactivity rules raise — is a plausible one. But it's important to note that even Justice Scalia, a firm critic of certain kinds of reliance on foreign practices, finds it proper to draw such distinctions, and to consider foreign practices in some situations.

I think critics of some Justices' use of foreign law — especially the shrillest critics, who denounce such use as a near betrayal of the Justices' oath — should keep these distinctions, and other similar ones, in mind. Thus, for instance, the reference to foreign attitudes in the Lawrence v. Texas majority may be different from the reference to such attitudes in the Grutter race preferences case, and still other uses of foreign practices might be treated differently still.

For more on this, see here, here.