In the case of Thompson v. Oklahoma in 1987, the U.S Supreme Court ruled that it was unconstitutional to execute individuals who were under 16 years old at the time they committed their crimes. The decision came after William Wayne Thompson, who was convicted for a murder he participated in when he was just 15 years old, appealed his death sentence. The court's majority opinion held that executing such young offenders violated "evolving standards of decency" and thus constituted cruel and unusual punishment as prohibited by the Eighth Amendment to the Constitution. This ruling set an important precedent regarding juvenile justice and capital punishment laws across America.

In the dissenting opinion for Thompson v. Oklahoma, Justice Scalia argued that there was no historical or contemporary consensus against executing 15-year-olds convicted of murder and thus it should not be considered cruel and unusual punishment under the Eighth Amendment. He criticized the majority's reliance on psychological and sociological research to determine a juvenile's culpability, arguing that such matters are better left to legislatures rather than courts. Furthermore, he contended that international law should have no bearing on interpreting U.S constitutional provisions. In his view, each state has its own unique moral standards which must be respected by federal courts in determining what constitutes "cruel" or "unusual". Therefore, if a state deems it necessary to impose capital punishment as a deterrent for grave crimes committed by juveniles aged fifteen years old or above then they should have every right to do so without interference from federal authorities.