Four justices said the court should continue a reexamination of the death penalty begun in earnest last year.
But the court passed up a chance to reopen the question of whether executing very young killers violates the Constitution's ban on "cruel and unusual punishment." Currently, states that allow the death penalty may impose it on killers who were 16 or 17 at the time of their crimes.
The dissenting justices called it a "shameful practice."
"The practice of executing such offenders is a relic of the past and is inconsistent with evolving standards of decency in a civilized society," Justice John Paul Stevens wrote, joined by Justices David Souter, Ruth Bader Ginsburg and Stephen Breyer.
The court refused to hear the case of a Kentucky man sentenced to death for abducting, sodomizing and killing a gas station attendant when he was 17. The body of the 20-year-old victim was left sprawled over the rear seat of her mother's car, with her jeans and underwear pulled to her ankles. She had been shot in the face.
Prosecutors said Kevin Nigel Stanford bragged about what he and two other teenagers had done.
Stanford, now 39, has been on death row since 1982. In 1989, the high court used Stanford's case to uphold juvenile executions.
Only the United States and a handful of other countries allow execution of juvenile killers, and Stanford's lawyers argued that such executions violate not only the Constitution but an international treaty signed by the United States.
Neither this case nor last term's landmark ruling on the mentally retarded address the constitutionality or morality of the death penalty as a whole.
Like the retardation question, the issue of juvenile killers turns on the individuals' capacity to understand their situation, and their level of culpability. Also like the retardation question, this one questions whether the country has changed its mind about what kind of punishment is appropriate.
The court relied heavily on the actions of state legislatures in deciding to ban executions of the retarded. On that issue, the court said the large number of states that had acted on their own to ban such executions showed that the nation no longer supported the practice.
"In the last 13 years, a national consensus has developed that juvenile offenders should not be executed," Stevens wrote in the dissent.
The court's refusal to hear the case was expected. A delay seemed likely because it would give more state legislatures a chance to do their own reexamination of the practice, much as they did with the retardation issue.
Currently, 16 of the 38 states that allow the death penalty prohibit it for those under 18. The federal government also prohibits the practice for juveniles prosecuted in federal court. Two states, Montana and Indiana, have enacted their prohibition laws since the court last considered the Stanford case in 1989.
"The evolving norms of decency have come to the point where we as a country have decided its no longer appropriate to execute the mentally retarded. I think the time has also come to reassess whether it is no longer appropriate to execute our children," said Margaret O'Donnell, a lawyer for Stanford.
This establishes two things about the current court, says CBSNews.com Legal Analyst Andrew Cohen.
One, there is clearly a block of four Justices that is willing to go much further in restricting the application of the death penalty in this country. And, two, that block has yet to bring that crucial FIFTH Justice into their camp. Which means that we aren't likely to see wholesale changes to death penalty law anytime soon.
When the Court last term prohibited the execution of mentally retarded people, it did so relying heavily upon a state trend away from those sorts of executions. This result today suggests that a majority on the court is not yet convinced that such a trend exists when it comes to the execution of 16- and 17-year-olds.
This is a defeat, says Cohen, for death penalty opponents who had hoped that a Supreme Court ruling last term prohibiting the execution of mentally retarded people would be extended to preclude the execution of people under the age of 18. And it is a sign from the Court that there won't necessarily be a continuous rollback of the death penalty anytime soon
In other Supreme Court action Monday:
Justices had been asked to overturn a ruling that expanded police powers and allowed the searches. They declined, without comment.
The state has argued it cannot be sued by people unhappy with Medicaid benefits, but lower courts refused to dismiss the lawsuit.
Justices declined without comment to hear the state's appeal. The court could have used the case to clarify state immunity in federal lawsuits. In a series of states rights cases, justices have broadened lawsuit protection for states.