Natural law is also called the law of “nature’, “reason” or “nature and reason”. Lord Mansfield once called it “principles of law, justice and humanity”. Blackstone acknowledged natural law’s immutability. Dr Johnson saw its rationality. Its modern credentials lie in Lord Radcliffe’s 1960 call never to lose touch with natural law or give up the belief that all positive law bears some relation to it. Lon Fuller saw in every school of natural law a coalescence between what the law is and what it ought to be. Hans Kelsen, although a legal positivist, saw the natural law beliefs underlying America’s Constitution. In 1825, with natural law at the forefront, the United States Supreme called slavery an institution of positive law against natural law. But in 1927, with natural law driven into solitary dissent, forced sterilization was approved by that court. Cicero spoke of right reason in harmony with nature, universal unchanging and everlasting. Pufendorf considered natural law essential to a good and peaceful society. Bao Gong saw social harmony’s need for something higher than positive law. Aquinas in the 13th century and Gustav Radbruch in 1945 addressed the dire consequences of ignoring natural law. This law, the Doctor told the Student, is written in our hearts, teaching what is to be done and what is to be fled. Under an unwritten constitution, serious legislative departure from natural law might lead to judicial revisiting of absolute parliamentary supremacy. Independent judicial stewardship of entrenched freedom and rights-friendly constitutions secure natural law-based human rights. The Universal Declaration of Human Rights flowed from the belief that world peace is best secured by respecting human rights worldwide. Natural law was, as Judge Tanaka said, before, and independent of, the State. Long before, Coke said. Francis Bacon spoke of what is “corroborated and confirmed by law, but is the work of the law of nature”. Natural law ideas exist among common lawyers, civilians, canonists and scholars of Islamic law. International law is, as Emmerich de Vattel said, the law of nature applied to States. Natural law and international law unite against the subjugation of one people by another. Professor Martin S Flaherty said that customary international law may prove more important than treaties to human rights protection. “The common law, now so called, is founded on the law of nature and reason”, Mr Justice Aston said. Throughout common law and equity, there exists a substratum of natural law. We see that in, for instance, commercial law and tort. Administering criminal justice with mercy is natural law. Natural law is a perspective from which pandemic lockdowns are viewed. We can, and should, integrate natural law and positive law. Modern judges have a role in making human law conform to natural law.