Hart’s solution to the problem that Kelsen identified is, however, very different. Hart claimed that wherever a legal system exists, there also exists a “rule of recognition” that specifies the criteria of legal validity that any rule must satisfy in order to count as a rule of that legal system. But a rule of recognition is not a Grundnorm, a transcendental presupposition of legal thought. It is rather a complicated psychosocial phenomenon (an instance of what Hart called a “social rule”) whose existence and content are established by the sociological fact that officials of the legal system converge on certain criteria of legal validity and by the psychological fact that such officials view those criteria as obligatory. Thus, the U.S. Constitution is a source of legal authority in the U.S. legal system because almost all judges treat constitutionality as a criterion of legal validity (a law that is unconstitutional is not enforced by the courts) and act and talk as if they have an obligation to do precisely that.
Hart’s positivist theory of law is, then, “impure”: contrary to Kelsen, Hart claimed that the normative character of law can be explained in terms of complicated facts about the behaviour and attitudes of officials of the legal system, primarily judges. To be sure, Hart agreed with Kelsen that laws may be morally unjustified, but, unlike Kelsen, he thought that the existence of law is, fundamentally, dependent on nothing more than the conventional practices of judges. If judges in the United States were to stop treating the Constitution as a criterion of legal validity, then it would cease to be such. Joseph Raz
Raz explored in greater depth than Hart or Kelsen the idea that law claims the right to tell citizens what they must do—what Raz called law’s claim to authority. But what is authority? Raz defended the “service conception” of authority, according to which law is genuinely authoritative insofar as it helps the subjects of the law to do what they really ought to do better than they would without the mediation of the law’s directives. Of course, many laws fail to satisfy this demanding standard, but Raz also argued that only a rule of recognition employing source-based criteria of legal validity—criteria such as “enacted by parliament” or “proclaimed by the king”—could possibly possess genuine authority. The reason, according to Raz, is that if what the law tells someone to do is not intelligible independent of the moral and other reasons on which it is based, then the law cannot possibly perform a service for its subjects. Raz’s version of legal positivism thus incorporated the idea that norms are legally valid—i.e., part of the law—only in virtue of their social source. In that respect, Raz recast themes from the command tradition of the early modern period, in particular the idea that law is a system of norms that play a special role in the practical reasoning of its subjects and, with Hobbes and Bentham, that the contents of those norms must be identifiable without recourse to controversial moral argument. Ronald Dworkin
Although legal positivism thus triumphed in the 20th century, it was not without critics. Ronald Dworkin, for example, argued that moral reasoning is essential for resolving difficult constitutional questions. Hart had never denied that claim, however; what he denied was only that such moral considerations were necessarily part of the law, unless they were also part of society’s rule of recognition. (Raz, as noted above, rejected the latter possibility: when judges rely on moral considerations, they are exercising discretion, not making decisions required by law.) Dworkin also argued that Hart’s account of the rule of recognition as a convergent practice of officials to which they took a critical reflective attitude could not explain why such officials had any obligation to comply with a rule so conceived. But it was never Hart’s aim to show that officials had an obligation to apply particular criteria of legal validity, only to explain the necessary conditions for the existence of a legal system. Hart recognized that officials might treat the rule of recognition as obligatory for many different kinds of reasons, and he also recognized that they might be wrong to do so.
In his later work Dworkin expanded on the idea that moral considerations figure in determining what the law is. He now argued that whatever follows from the best “constructive interpretation” of the source-based norms of the legal system (such as legislative enactments and prior court decisions) constitutes the law of that system. A constructive interpretation in Dworkin’s technical sense is one that seeks both to explain the previous source-based norms in terms of some more-general moral principles about fairness and justice for which they stand and to rely on those explanatory moral principles to provide an attractive moral justification for the legal system as it exists. Dworkin’s view, which attracted almost no adherents, had the odd consequence that no one might know what the law of the legal system is, since no one might yet have thought of the best constructive interpretation. Hart interpreted Dworkin as simply describing the rule of recognition of Anglo-American and other common law legal systems, in which judges do try to produce a kind of “principled coherence” between their decision in the current case and prior court decisions. John Finnis
John Finnis took a more-ambitious philosophical tack against positivism than Dworkin did. He argued that any theory of a social phenomenon, including law, must identify its “central” cases, since the goal of any theory is to describe the central or important features of the subject matter in question. The central cases of law, according to Finnis, are those in which there exists a genuine moral obligation to obey the law. Finnis thus treated as the task of legal theory the identification of those characteristics of legal systems that are so morally good as to justify anyone’s obedience. Hart agreed that the philosophy of law should focus on central cases, but he also believed, contrary to Finnis, that the central cases could be identified without regard to their moral quality. Indeed, Hart’s ambition was to explain the nature of laws and legal systems that ordinary people would typically identify as such. The problem of the Nazis
Finnis’s approach highlighted a central problem looming over legal philosophy beginning in the second half of the 20th century: namely, what to say about the Nazis. By all appearances, the Nazis had a legal system, one that authorized the confiscation of life, property, and liberty on the basis of religion and ethnicity. Yet after World War II, Nazi officials were tried, convicted, and sometimes executed for their “lawful” actions. For Finnis and some other natural-law theorists, Nazi law was not a “central case” of law but a defective instance of it; thus, it was proper to prosecute Nazi officials for acting in grossly immoral ways. By contrast, Hart and other legal positivists, in the spirit of Hobbes and Bentham, sought to separate the question of whether the Nazis had law—it certainly looks as though they did, in almost all respects—from the question of whether their laws were just (they were not) and whether the morally grotesque character of the actions of Nazi officials should warrant punishment, even though the actions were lawful. For Hart, distinguishing between the question “What is law?” and the question “What is morally right?” has the salutary effect of reminding people that not all laws are morally good and that officials may be held accountable even for their lawful actions when those actions are sufficiently wicked. Realism