Public law

Lore & Background

The distinction between public law and private law dates back to Roman law, where the Roman jurist Ulpian first noted it. Ulpian argued in the Institutes that 'public law is that which respects the establishment of the Roman commonwealth, private that which respects individuals' interests.' Roman Law conceived of law as relationships between persons and persons, persons and things, and persons and the State, with public law consisting of the latter. However, Roman lawyers devoted little attention to this area, focusing largely on private law. The distinction was of great importance in Teutonic society, as noted by German legal historian Otto von Gierke, who defined the Teutons as the fathers of public law. Drawing a line between public and private law largely fell out of favor in the ensuing millennium. Medieval jurists saw a concern with the Roman conception of the res publica inherent in the legal fiction of the king's two bodies, but legal philosophers were largely theologians operating within Canon Law, concerned with distinctions between divine, natural, and human law. The public/private divide returned in the 17th and 18th centuries with the emergence of the nation-state and new theories of sovereignty. Claims by monarchs and parliaments to unrestrained power spurred attempts to establish a distinctly private sphere free from encroaching State power. For many years, public law occupied a marginal position in continental European law, with private law considered general law and public law consisting of exceptions. It was not until the second half of the twentieth century that public law began to play a prominent role through the constitutionalization of private law and the development of administrative law and functional fields such as labor law, medical law, and consumer law. This blurred the distinction but elevated public law from its once-marginal state.

Reader's Guide

Public law is significant as a foundational category of legal systems, distinguishing the asymmetric relationship between the state and individuals from private relationships. Its roots in Roman law, particularly through Ulpian's work, established a framework that later influenced both civil-law and common-law traditions. The distinction is largely functional rather than factual, classifying laws according to which domain activities and participants best fit. The borderline between public and private law is not always clear, as seen when an individual contracting with the government for a service usually falls within private law despite state involvement. Public law's legacy includes the development of constitutional law, which lays out the foundations of the state and postulates the rule of law; administrative law, which regulates bureaucratic procedures and defines powers of agencies; criminal law, which relates to crime and punishment; and tax law, which became an area of public law in the 17th century. The theoretical distinction has been extensively discussed in German-language legal literature, producing theories such as the interest theory from Ulpian, elaborated by Montesquieu in The Spirit of the Laws. Public law's elevation in the twentieth century acknowledged that few areas of law are free from potential state intervention, making it a central element of modern governance.

Did You Know?

• The distinction between public and private law was first made by Roman jurist Ulpian.
• Public law comprises constitutional law, administrative law, tax law, criminal law, and all procedural law.
• The borderline between public and private law is not always clear and is largely functional rather than factual.
• Tax law became an area of public law in the 17th century as a consequence of emerging theories of sovereignty.

The Public-Private Divide and Its Jurisdictional Variations

Public law occupies the domain of government and society, encompassing constitutional law, administrative law, and criminal law. This stands in contrast to private law, which governs disputes between individual parties in areas such as contracts, property, torts, delicts, and commercial matters. The sharpness of this boundary, however, is not uniform across legal traditions. In civil law countries—particularly those that maintain a separate system of administrative courts—the public-private distinction is drawn with considerable force. By contrast, common law jurisdictions tend to blur this line, with the divide being far less pronounced. This structural difference reflects deeper institutional commitments: civil law systems rely on codified and consolidated statutes produced by a legislature or central body, while common law systems empower judges to create binding case law through precedent, though higher courts or legislatures can overturn such decisions. The result is that what counts as public regulation versus private ordering shifts depending on which jurisdictional tradition one inhabits.

The Architecture of Law-Making

The creation of binding rules in any society flows through multiple channels. A legislature enacts statutes; the executive branch issues decrees and regulations; and in common law jurisdictions, judges generate precedent through their decisions. In an autocratic system, a single ruler may consolidate all three functions within their realm. The process is not free-floating: a constitution, whether written or tacit, and the rights encoded within it, exert influence over how laws are crafted. Beyond mere rule-making, law operates as a mediator of human relations and shapes politics, economics, history, and society in numerous ways. It has been variously characterized as a science and as the art of justice. The precise definition of what law actually is remains a subject of longstanding scholarly debate, with no single formulation commanding universal acceptance across the field.

The Definitional Quagmire and Competing Theories

The question of what law fundamentally is has resisted a simple answer for centuries. Glanville Williams observed that the word's meaning shifts depending on context, noting that early customary law and municipal law carry two irreconcilable senses. Yet Thurman Arnold insisted the struggle to define should never be abandoned, even while acknowledging its impossibility. Competing theorists have offered divergent frameworks: H. L. A. Hart described law as a system of rules; John Austin framed it as a sovereign's command backed by sanctions; Ronald Dworkin treated it as an interpretive concept aimed at justice; Joseph Raz saw it as an authority mediating interests; and Oliver Wendell Holmes reduced it to predictions of what courts will actually do. Thomas Aquinas, in his Treatise on Law, proposed a rational ordering concerned with the common good, blending positivist and naturalist elements.

Law, Morality, and the Positivist-Naturalist Divide

A persistent tension runs through legal philosophy: does law incorporate morality, or is it entirely separate from it? Austin and Bentham, following David Hume, argued for strict positivism—that real law is wholly distinct from moral oughts—and warned against conflating what is with what ought to be. Natural lawyers like Rousseau countered that law reflects essential, unchangeable moral laws of nature, a concept rooted in ancient Greek philosophy and revived through Aquinas's writings. Hugo Grotius sought a middle path, grounding natural law in both social impulse and reason. Kant demanded that laws be chosen as though they should hold as universal natural laws, though Nietzsche rejected this, insisting law emanates from the will to power and resists moral labeling. His major opponent, Carl Schmitt, rejected both positivism and the rule of law, advocating instead a jurisprudence of the exception that denied legal norms could encompass all political experience.