SWING SHIFT.(Anthony Kennedy of Supreme Court)

Few Justices in recent history have arrived at the Supreme Court from a more provincial background than Anthony Kennedy. Before he moved to Washington, seventeen years ago, his professional life had been spent almost entirely in Sacramento. He was born there in 1936, and when his father, a lawyer who had his own practice, died two years after Kennedy graduated from Harvard Law School, he returned home to take over the family business. When President Reagan nominated him to the Supreme Court, in 1987, Kennedy was fifty-one years old and still lived in the house where he grew up.

His inclinations were hardly those of an insular man, however. While Kennedy was a teen-ager, his uncle, an oil driller, hired him to work summers on rigs in Canada and Louisiana. Before he graduated from college, he spent several months studying at the London School of Economics, where he was struck by the range of student opinion and the vehemence of political debate. "At the political union, you had to sit in the room according to your place on the ideological spectrum, and, to give you an idea of what it was like, the Communists--the Communists!--were in the middle," Kennedy recalled recently. "It was a different world, and I loved it." As an attorney in private practice, he maintained his father's ties with California's Republican Party; in 1973, he volunteered to draft a tax-cutting referendum for Governor Reagan, which lost at the polls. At the same time, he obtained a license to practice law in Mexico and helped a client establish one of the first maquiladoras--American-owned factories--there. While serving as a judge on the United States Court of Appeals for the Ninth Circuit, in the late nineteen-seventies, he accepted an appointment from Chief Justice Warren Burger as supervisor of the territorial courts in the South Pacific, which entailed travelling to Guam, Palau, Saipan, American Samoa, Australia, New Zealand, and Japan.

In fact, Kennedy has a passion for foreign cultures and ideas, and, as a Justice, he has turned it into a principle of jurisprudence. Over the past two years, he has become a leading proponent of one of the most cosmopolitan, and controversial, trends in constitutional law: using foreign and international law as an aid to interpreting the United States Constitution. Kennedy's embrace of foreign law may be among the most significant developments on the Court in recent years--the single biggest factor behind his evolution from a reliable conservative into the likely successor to Sandra Day O'Connor as the Court's swing vote. Kennedy continues to oppose racial preferences and to argue for expansive Presidential powers. He was a principal author of the unsigned majority opinion in Bush v. Gore. But he also wrote the two most important pro-gay-rights decisions in the Court's history and has at least tentatively affirmed his support for Roe v. Wade. Conservatives regard these decisions as a betrayal. In 2003, James Dobson, the founder and director of the influential evangelical group Focus on the Family, called Kennedy "the most dangerous man in America."

The United States Supreme Court has made references to foreign law since the earliest days of the Republic. During the tenure of Chief Justice John Marshall, the Court was often called on to interpret treaties and weigh controversies involving ships on the high seas, and the Justices frequently cited the laws of other nations in their decisions. In 1829, for example, Marshall analyzed both Spanish and French law to settle a claim by an American who had bought a parcel of land once owned by Spain and later included in the Louisiana Purchase. Contemporary commercial disputes also cross borders, and the Justices rely on foreign and international law, as well as on American statutes, to adjudicate them. In the past two years, the Court has considered such questions as whether Mexican trucks must abide by American safety rules under nafta, whether the American family of a Holocaust victim could recover art seized by the Nazis in Austria, and whether a United States district court should compel the American computer-chip-makers AMD and Intel to provide documents to each other in a European antitrust dispute. "When it comes to interpreting treaties or settling international business disputes, the Court has always looked to the laws of other countries, and the practice has not been particularly controversial," says Norman Dorsen, a professor at New York University Law School.

However, beginning in the late nineteen-nineties, the Court's more liberal members began citing foreign sources to help interpret the Constitution on basic questions of individual liberties--for which the laws of foreign democracies tend to be more progressive than those at home. In 1999, Justice Stephen Breyer protested the Court's refusal to hear the appeal of a prisoner who argued that spending more than two decades on death row amounted to cruel and unusual punishment, and thus violated the Eighth Amendment. Quoting legal opinions from Jamaica, India, Zimbabwe, and the European Court of Human Rights, Breyer observed in a dissenting opinion in Knight v. Florida that "a growing number of courts outside the United States . . . have held that lengthy delay in administering a lawful death penalty renders ultimate execution inhuman, degrading or unusually cruel." More recently, in an opinion concurring with the Court's decision to uphold the affirmative-action program at the University of Michigan Law School, Justice Ruth Bader ...