The Supreme Court, in a plurality opinion by Justice Stevens, utilized the “evolving standards of decency” doctrine to conclude that the "cruel and unusual punishment" prohibition of the Eighth Amendment forbids the execution of a person who is even one day under 16-years of age at the time of his or her offense.
This case is activist because the majority relies on the so-called Living Constitution to make the Constitution comport with their self-described enlightened sensibilities. They entirely side-stepped any discussion of the original meaning of the Eighth Amendment and instead claim to look to the “evolving standards of decency that mark the progress of a maturing society.” The majority ignores the fact that there is overwhelming evidence in both historical practice and the common law that the Eighth Amendment was not originally meant to entail a prohibition against the execution of anyone under 16.
The “evolving standards of decency” doctrine has become part and parcel of Eighth Amendment jurisprudence. In his dissent, Justice Scalia points out the danger of this doctrine: “[T]he risk of assessing evolving standards is that it is all too easy to believe that evolution has culminated in one's own views. To avoid this danger we have, when making such an assessment in prior cases, looked for objective signs of how today's society views a particular punishment. The most reliable objective signs consist of the legislation that the society has enacted. It will rarely if ever be the case that the Members of this Court will have a better sense of the evolution in views of the American people than do their elected representatives.”
Reasonable minds can disagree as to the policy at issue here, which is why we have legislatures to weigh the policy factors. But here, the Court used the “evolving standards” doctrine as a tool to convert their own predilections into the law.