Definition
Jus pretorium (also spelled jus prætorium) is a term from Roman and civil law referring to the body of law developed and applied by the praetor — the magistrate charged with administering justice in Rome — as distinguished from the leges, the formal statutory enactments of the Roman people. It denotes the discretionary authority the praetor exercised to aid, supplement, or correct the civil law (jus civile) in the interest of public benefit and equitable outcome.
Where the strict civil law produced harsh or unjust results, or simply failed to address a situation, the praetor could intervene through edicts, granting remedies or recognizing rights not formally acknowledged by the written law. Over time, the accumulated edicts of successive praetors formed a coherent body of doctrine that operated alongside — and often in tension with — the formal civil law.
Common Confusion
Jus pretorium is closely related to, and frequently used interchangeably with, jus honorarium. Black's (2nd Ed.) treats the terms as synonymous, noting that jus pretorium is "called also honorarium." The distinction, where one is drawn, is that jus honorarium is the broader category encompassing the law introduced by all magistrates holding honor (office), including the aediles, while jus pretorium refers specifically to the praetor's contribution. Researchers should not assume that a historical source using one term excludes the other.
Jus pretorium must also be distinguished from jus precarium, a separate Roman law concept referring to a precarious right — a possessory interest held at the will of another — which shares only the "jus pre-" prefix and no substantive connection.
Why It Matters in Research
This term appears most frequently in Roman law scholarship, civil law jurisdiction materials, and in English common law treatises that trace equity's intellectual ancestry. Blackstone's Commentaries (3 Bl. Comm. 49) invokes jus pretorium when drawing the analogy between the Roman praetor and the English Court of Chancery — a comparison that shaped how early American legal writers understood equitable jurisdiction. Researchers working in equity jurisprudence, especially materials predating the merger of law and equity, will encounter this term as part of that foundational argument.
The key research trap is treating jus pretorium as a static category. In Roman law history, the praetor's edict evolved considerably — from ad hoc interventions to a largely fixed text (the edictum perpetuum, codified under Hadrian). Sources from different periods may describe the term with different emphases: early sources stress discretion and flexibility; later sources stress the settled doctrinal content of the praetorian corpus. A treatise writer citing jus pretorium in 1800 may be invoking the philosophical concept of judicial equity power rather than making a precise claim about Roman law.
In civil law jurisdictions, traces of the praetorian tradition appear in discussions of judicial interpretation and gap-filling, though the term itself is rarely used in modern statutory or case materials. Comparative law researchers drawing lines between civil and common law equity traditions will find this term at the intersection.
Historical Dictionary Support
Black's Law Dictionary (2nd Ed.) offers a compact but accurate entry, drawing on two sources: Blackstone's Commentaries (3 Bl. Comm. 49) for the praetor's discretion as distinct from leges, and the Digest (Dig. 1, 1, 7) for the formulation that jus pretorium was introduced "for the purpose of aiding, supplying, or correcting the civil law for the public benefit." These two framings are complementary rather than competing — Blackstone emphasizes the praetor's institutional role, while the Digest formulation captures the substantive function.
What the Black's entry does not convey is the historical arc: jus pretorium was not a permanent feature of Roman governance but a product of the Republic and early Empire. Its vitality declined as imperial rescripts and constitutions displaced magisterial discretion as the primary source of legal development. Researchers should be aware that treatise writers invoking jus pretorium in the 18th and 19th centuries were often engaged in a jurisprudential argument — about the legitimacy of judicial lawmaking — rather than providing a descriptive account of Roman practice.
No significant divergence among the available historical dictionary sources exists here; the scarcity of entries reflects the term's status as specialized civil law vocabulary rather than common law currency.
Jurisdictional Note
The term has no operative legal meaning in modern common law jurisdictions. It functions as intellectual history in Anglo-American legal writing and as comparative law vocabulary. Civil law scholars in France, Spain, and Latin America may encounter derivative concepts without the Latin label.