Definition
Jus praetorium (also rendered jus prjbtortum in certain older typeset editions, reflecting a compositor's contraction) refers to the body of law introduced and developed by the Roman praetor through the exercise of his judicial discretion, as distinguished from the leges — the standing statutory law of Rome. It describes the praetor's authority to aid, supplement, or correct the civil law (jus civile) in the interest of equity and public benefit. The praetor accomplished this primarily through the edicts he issued upon taking office, which over time accumulated into a substantial body of enforceable legal principle operating alongside, and sometimes overriding, the strict civil law. Jus praetorium is functionally synonymous with jus honorarium, reflecting the honorary or magisterial character of the praetor's office.
Common Confusion
The terms jus praetorium and jus honorarium appear interchangeably in both Roman legal sources and subsequent commentary. Blackstone uses jus praetorium; the Digest uses both. Neither is incorrect, but researchers relying on English common law commentators will more often encounter jus praetorium, while civilian and continental sources tend toward jus honorarium. Do not conflate either term with jus civile (the strict civil law) or with jus gentium (the law of nations) — these are distinct layers of the Roman legal system with different sources and authority.
Why It Matters in Research
This term appears almost exclusively in historical and comparative legal scholarship. Researchers will encounter it most often in three contexts: (1) commentary on Roman law in English legal treatises, particularly Blackstone's Commentaries and works drawing on Justinian's Digest; (2) historical analyses tracing the equity jurisdiction of English courts, where scholars drew an explicit analogy between the Roman praetor's corrective function and the English Chancellor's development of equity to soften the rigidity of common law; and (3) civilian scholarship on the sources and layers of Roman private law.
The analogy to English equity is the most consequential navigational point. When Blackstone and later commentators cite jus praetorium in the context of English legal development, they are typically arguing that Chancery equity stands in structural relation to the common law precisely as praetorian law stood to the jus civile — a parallel correction mechanism operating within the same system. Researchers tracing the intellectual history of equity jurisdiction will find this parallel invoked repeatedly and should understand jus praetorium as the Roman half of that comparison.
A typographic caution: early printed editions of Black's and other historical dictionaries frequently rendered Latin terms with contracted or corrupted letterforms due to compositing conventions. The form "Jus Prjbtortum" appearing in certain editions is a printing artifact of "Jus Praetorium." Researchers searching historical indices or digitized text should be alert to variant spellings and failed OCR transcriptions of this and similar Latin terms.
Historical Dictionary Support
Black's Law Dictionary (2nd Ed., Supplemental) defines the term by reference to Blackstone (3 Bl. Comm. 49) and the Digest of Justinian (Dig. 1, 1, 7), identifying it as the praetor's discretionary authority introduced for the purpose of aiding, supplying, or correcting the civil law for the public benefit. Black's expressly equates jus praetorium with jus honorarium, treating them as alternate names for the same concept.
The Digest passage cited — attributed to Papinian — is the foundational source: it distinguishes jus praetorium as that which the praetors introduced to aid, supplement, or correct the civil law in the public interest. This characterization is consistent across Roman legal scholarship and is not disputed in the historical dictionaries.
What the historical dictionaries do not adequately address is the developmental character of jus praetorium. The praetor's edict was initially issued anew each year, but by the classical period the edict had become largely standardized — ultimately codified under Hadrian as the Edictum Perpetuum. Researchers looking for the dynamic, evolving phase of praetorian law will need to go beyond the dictionary definitions to primary Romanist scholarship.
Jurisdictional Note
Jus praetorium is a term of Roman law with no direct application in any modern common law jurisdiction. Its relevance in Anglo-American legal research is historical and analogical — primarily in equity jurisprudence and comparative law scholarship.