The state of Louisiana and the Justice Department had asked the court to reconsider the 5 to 4 decision because the court was not made aware of what they consider a crucial element: that Congress in 2006 made child rape a capital offense under military law.

No one presented that fact — it seems none of the parties knew at the time that it existed — when the court said in June that there was no evidence of a national consensus in favor of putting child rapists to death. The court also found that in its “independent judgment,” child rape could not be compared to murder in terms of warranting the death penalty.

High Court Will Not Reconsider Decision on Child Rape – washingtonpost.com