Court of public opinion?

Whether or not death sentences for juvenile criminals are cruel and unusual punishment is a legitimate constitutional issue. In its decision this week saying executions of juveniles are unconstitutional, the U.S. Supreme Court went far beyond the Constitution in its majority opinion.

Writing for the five-justice majority, Justice Anthony Kennedy included a remarkable -- and questionable -- justification. He said the court's ruling reflected a "national consensus" against the death penalty for juveniles, and he said the court must acknowledge "the overwhelming weight of international opinion." Both of those justifications are poor excuses, and neither is a constitutional issue. (For further reflections, see The Wall Street Journal's editorial elsewhere on this page.)

A 1989 ruling by the same court upheld the constitutionality of death sentences for 16- and 17-year-olds. That ruling, in effect, upheld the right of states to impose death penalties. Nineteen states chose to do so. It was a Missouri case involving a Cape Girardeau jury that led to this week's Supreme Court ruling. The jury found a juvenile, who was 17 when he murdered a neighbor, guilty and decided he should be executed. The Missouri Supreme Court overturned the sentence in spite of the U.S. Supreme Court's ruling that such executions were constitutional.

With this latest ruling, states have lost another basic right of self-governance. That the decision comes with the baggage of international opinion and a national consensus -- which clearly was not held by 19 states -- establishes a dangerous arena for judicial activism that has no constitutional merit.

What next? A national vote -- or, worse yet, U.N. resolutions -- on tough cases?