In Roper v. Simmons, Justice O'Connor, even while agreeing with Justice Scalia on the outcome, chides him for refusing to review foreign views of the subject. She dissents anyway because she doesn't believe there is an American consensus against the juvenile death penalty, and, for her, even the existence of an international consensus against it is insufficient to justify declaring it unconstitutional. Here is O'Connor's response to Scalia:
I disagree with JUSTICE SCALIA’s contention, post, at 15–22 (dissenting opinion), that foreign and international law have no place in our Eighth Amendment jurisprudence. Over the course of nearly half a century, the Court has consistently referred to foreign and international law as relevant to its assessment of evolving standards of decency. See Atkins, 536 U. S., at 317, n. 21; Thompson, 487 U. S., at 830–831, and n. 31 (plurality opinion); Enmund, 458 U. S., at 796–797, n. 22; Coker, 433 U. S., at 596, n. 10 (plurality opinion); Trop, 356 U. S., at 102–103 (plurality opinion). This inquiry reflects the special character of the Eighth Amendment, which, as the Court has long held, draws its meaning directly from the maturing values of civilized society. Obviously, American law is distinctive in many respects, not least where the specific provisions of our Constitution and the history of its exposition so dictate. Cf. post, at 18–19 (SCALIA, J., dissenting) (discussing distinctively American rules of law related to the Fourth Amendment and the Establishment Clause). But this Nation’s evolving understanding of human dignity certainly is neither wholly isolated from, nor inherently at odds with, the values prevailing in other countries. On the contrary, we should not be surprised to find congruence between domestic and international values, especially where the international community has reached clear agreement—expressed in international law or in the domestic laws of individual countries—that a particular form of punishment is inconsistent with fundamental human rights. At least, the existence of an international consensus of this nature can serve to confirm the reasonableness of a consonant and genuine American consensus. The instant case presents no such domestic consensus, however, and the recent emergence of an otherwise global consensus does not alter that basic fact.