I admit that this makes me nervous

Today the Supreme Court declared that the Eighth Amendment (which prohibits cruel and unusual punishment) bars the execution of persons who were under 18 at the time they committed their crime.

I don't think executing juveniles is a very good idea, so I don't have a problem with the result per se.  But how the Court got there is a tad worrisome.  This line from Justice Kennedy's opinion pretty much sums it up:

We then must determine, in the exercise of our own independent judgment, whether the death penalty is a disproportionate punishment for juveniles.

So the Court seems to have decided that the definition of "cruel and unusual punishment" is determined, quite literally, by the views of five current members of the Court.  Justice Scalia, predictably, goes off on this, asking rhetorically, "By what conceivable warrant can nine lawyers presume to be the authoritative conscience of the Nation?"  I'm no Scalia fan, but it's hard to argue with that one.  The Court's approach does not strike me as a terribly reliable way to build up a consistent body of jurisprudence, nor does it strike me as what John Marshall had in mind when he famously declared in 1803 that "It is emphatically the province and duty of the judicial department to say what the law is."

Some, including some of my co-bloggers with the initials B.N., might say to me, "Aha, see?  This is what comes of conferring too much power on unelected life-tenured individuals - they inevitably will simply bend the law to suit their whims.  It may start with the Eighth Amendment, but it will never end there."  I, however, am an optimist, and I continue to believe that the Court generally operates under constraints, both internal and external, that prevent it from going that far (with some notable exceptions).  But today's decision is undeniably a step in the "because we say so" direction.