In Roper v. Simmons, the Court unequivocally affirms the use of comparative constitutionalism to interpret the Eighth Amendment. It does not, however, provide an obvious theoretical basis to justify the practice. This Article searches for a theory to explain the comparativism in Roper using the theories advanced in the author's previous scholarship. It concludes that of the colorable candidates, natural law constitutionalism is the most plausible explanation, with the attendant problems associated therewith. The Article concludes with an analysis of the possible ramifications of the Court's comparative approach, suggesting that it may be pursuing a Constitution that is in international equipoise, with international values distributed liberally throughout our jurisprudence to ensure foreign and domestic equilibrium.