AGAINST FOREIGN LAW ROBERT J. DELAHUNTY ∗ AND JOHN YOO ** In recent years, several Supreme Court Justices have looked to the decisions of foreign and international courts for guidance in interpreting the U.S. Constitution. This practice has occurred in several controversial, high‐profile cases. Roper v. Simmons 1 outlawed application of the death penalty to offenders who were under eighteen when their crimes were committed. Law‐ rence v. Texas 2 struck down a state law that criminalized homo‐ sexual sodomy. Atkins v. Virginia 3 held against the execution of mentally retarded capital defendants. All three cite foreign and international precedents. In Roper, the Court, per Justice Kennedy, found it “proper that we acknowledge the overwhelming weight of interna‐ tional opinion against the juvenile death penalty .... The opin‐ ion of the world community, while not controlling our outcome, does provide respected and significant confirmation for our own conclusions.” 4 The Court relied on a provision of the United Nations Convention on the Rights of the Child—a treaty the United States has not ratified—and on amicus briefs by the European Union and interested foreign observers. 5 In Lawrence, Justice Kennedy’s majority opinion cited decisions of the European Court of Human Rights to conclude that prohib‐ iting homosexual sodomy is at odds with the current norms of ∗ Associate Professor of Law, University of St. Thomas School of Law. ** Professor of Law, University of California, Berkeley School of Law (Boalt Hall); Visiting Scholar, American Enterprise Institute. We received valuable comments on earlier versions of this paper at a faculty workshop at the William & Mary School of Law and at the Federalist Society’s 2004 National Symposium. Jesse Choper and John McGinnis provided helpful comments. 1. 125 S. Ct. 1183 (2005) (plurality opinion). 2. 539 U.S. 558 (2003). 3. 536 U.S. 304 (2002). 4. Roper, 125 S. Ct. at 1200. 5. Id. at 1199 (citing United Nations Convention on the Rights of the Child art. 37, Nov. 20, 1989, 1577 U.N.T.S. 3, 28 I.L.M. 1448, 1468–70).