Supreme Court Justice Antonin Scalia says many disagreeable things, but it's hard to dispute one of the points he made in his dissent in Roper v. Simmons. "It is entirely consistent to believe that young people often act impetuously and lack judgment, but, at the same time, to believe that those who commit premeditated murder are--at least sometimes-just as culpable as adults."

Scalia's point--that a 17-year-old can be as morally liable as an 18-year-old--is, we think, undisputable. The question then is: What to do about it?

A closely divided Supreme Court gave its answer March 1 when, by a vote of 54, it ruled that the death penalty for juveniles was a violation of the Constitution's Eighth Amendment prohibition on "cruel and unusual punishment." The decision was in keeping with recent precedents. In 1988, the court ruled that executing those who were 16 or under at the time they committed their crime was unconstitutional; and, in June 2002, it said that the mentally retarded could not be subject to the ultimate penalty.

Still, the Scalia dissent (in which Chief Justice William Rehnquist and Associate Justice Clarence Thomas joined) rankles. True, society draws lines around an 18th birthday and declares that what a teenager can't do one day (such as vote or leave home and rent an apartment) he or she can do the next. Nevertheless, it seems cruel for society to say that a murderer of 17-years-and-364-days-of-age faces one penalty, while a commensurate crime by an 18-year-old faces a much harsher sanction.

It seems cruel because it is cruel. …