In his 2021 book, “The Decline of Natural Law,” the legal historian Stuart Banner observed that the recruitment of natural law by opposing sides on contentious social issues contributed to increasing doubt about its existence. By the early twentieth century, lawyers and judges considered natural law to be irrelevant to the legal system, and the language all but disappeared from legal arguments and decisions. Justice Oliver Wendell Holmes, Jr., bitingly mocked people’s belief in natural law as a “naïve state of mind that accepts what has been familiar and accepted by them and their neighbors as something that must be accepted by all men everywhere.” But the rise of totalitarianism and fascism in Europe in the nineteen-thirties, in constitution-bound states, provoked American lawyers to revisit the question of whether an unjust law was to be considered law at all. Many reflected, in particular, on the evil that Nazi Germany had accomplished through legalism. Lon Fuller argued, after the Second World War, that the Nazi regime’s violation of law’s “inner morality” had made it cease to be a true legal system.
When the Supreme Court, in Brown v. Board of Education, unanimously reversed Plessy, in 1954, it conspicuously avoided mentioning natural justice, higher principles, or moral values. Yet it admitted that Brown’s central holding, that “separate educational facilities are inherently unequal” and thus unconstitutional, did not flow from the Fourteenth Amendment’s original meaning. The same Congress had approved both the amendment’s text and the segregated schools of Washington, D.C. The civil-rights struggle was shot through with natural-law thinking, as Martin Luther King, Jr., made clear in his “Letter from Birmingham Jail.” He identified Thomas Aquinas as his source for the idea that “an unjust law is a human law that is not rooted in eternal law and natural law,” and that “a just law is a man made code that squares with the moral law or the law of God.”
As Congress passed landmark civil-rights legislation in the nineteen-sixties, the contest in the Supreme Court over natural law moved to concepts of autonomy and privacy. In 1965, the Court held, in Griswold v. Connecticut, that the application to married couples of a criminal ban on contraceptives was unconstitutional because of a fundamental right to privacy that was not laid out in specific words of constitutional text. Justice William O. Douglas, largely regarded as one of the most liberal Justices in history, wrote for the Court, which found the right in “penumbras, formed by emanations” from a number of Bill of Rights provisions. His fellow-liberal Justice Arthur Goldberg pointed to the Ninth Amendment, which provides that “the enumeration, in the Constitution, of certain rights, shall not be construed to deny or disparage others retained by the people.” Justice John Marshall Harlan II, a conservative, took a more moral-philosophical approach, saying that a law that “violates basic values ‘implicit in the concept of ordered liberty’ ” violates the Fourteenth Amendment’s due-process clause. In an earlier case, Harlan had explained that “due process has not been reduced to any formula; its content cannot be determined by reference to any code.” The meaning of “liberty,” he wrote, “cannot be found in or limited by the precise terms of the specific guarantees.” The meaning of the Constitution, in his view, was found in its broader purposes, not its text.
In the Griswold majority, the splits among Justices about the legal basis for the right to privacy revealed how contested it was from the start. In a dissent, the liberal Justice Hugo Black, who had prefigured modern originalism by several decades by championing plain text and original intent, rebuked his colleagues for relying on a “mysterious and uncertain natural law concept”—much as Justice Iredell had critiqued Justice Chase in the eighteenth century. But the right to privacy flourished. Justice Harlan’s approach to substantive due process became the foundation for Roe v. Wade, which declared that, although “the Constitution does not explicitly mention any right of privacy,” the right in the Fourteenth Amendment was “broad enough to encompass a woman’s decision whether or not to terminate her pregnancy.”
The conservative legal movement’s reaction to the fundamental-rights decisions of the sixties and seventies was to cry foul—accusing the Court of declaring those rights to be based on judges’ moral values rather than a neutral and fair reading of law. The concern was not limited to conservatives. One of the most important liberal constitutional scholars, John Hart Ely, who was pro-choice, called Roe “a very bad decision” because “it is not constitutional law and gives almost no sense of an obligation to try to be”—a line that became useful fodder for Justice Samuel Alito in overruling Roe, in 2022.
