When no rule fits the case, do judges find the law or make it?

Legal philosophers still disagree, and a nineteenth-century case shows why. Take Riggs v. Palmer, decided in New York in 1889. In 1882 sixteen-year-old Elmer Palmer, fearing his grandfather might change his will, poisoned him, knowing he would inherit a large estate. A criminal law existed to punish the murder, but no statute in probate or criminal law invalidated Elmer's claim to the estate. The court nonetheless ruled five to two against him, reasoning that tenets of universal law and maxims would be violated by letting him profit from his crime. Judge Gray dissented: a court cannot create or imagine statutes to obtain a morally pleasing result.

H. L. A. Hart's theory of legal positivism, set out in The Concept of Law (1961), says that laws are rules made by humans, with no inherent or necessary connection between law and morality. When a rule's words run out, he argued, there is a "penumbra". A law about "vehicles" clearly covers an automobile, but an airplane or a motorcycle is a penumbra case, where human interpretation decides. On the positivist account, judges there decide which application is the best social policy.

Ronald Dworkin used Riggs against Hart. The case, he argued, did not lie at the edge of the rules; it was clearly central, and yet the court did not simply apply the rule. His own theory, law as integrity, treats law as a "single coherent scheme of principle". It leads to his right answer thesis: even where legal rights are controversial, there is a right answer as a matter of law that the judge must discover, and judges do not have discretion in hard cases.

Critics answer that the law is full of gaps and inconsistencies, and that even principles may be insufficient to solve a hard case. The story has a twist: Hart, who remembered Dworkin's Oxford examination, promoted his candidacy, and in 1969 Dworkin succeeded him in the Chair of Jurisprudence at Oxford.