Definition
In civil law, the *mandatarius* is the party who receives and undertakes to carry out a mandate — that is, an agency or commission conferred by another (the mandator or mandans) without compensation. The mandatarius corresponds, in substance, to the modern concept of a gratuitous agent: one who accepts a task on another's behalf but receives no fee for doing so. The term is the Latin form of what English common law developed into the "mandatory" or "mandatary." The mandatarius is bound by the scope of the commission given and may not lawfully exceed it.
Common Confusion
MANDATARIUS vs. MANDATORY (English form): The Latin *mandatarius* and its anglicized derivative *mandatory* (or *mandatary*) are functionally synonymous in legal usage, but researchers encounter both spellings across sources depending on the era and the degree of latinization preferred by the author. *Mandatory* in this agency sense is not to be confused with the modern adjective *mandatory* meaning "obligatory" or "compulsory" — a wholly separate word that happens to share spelling. A researcher encountering *mandatory* in a pre-nineteenth-century civil law or equity treatise should read it as a noun meaning "one who holds a mandate," not as a descriptor of something required.
Why It Matters in Research
This is a term researchers will encounter in civil law sources, Roman law commentary, Scottish law materials, Louisiana jurisprudence, and equity treatises — rarely in English common law texts, where agency doctrine developed along different lines without borrowing the Latin terminology.
The key navigational point is the maxim embedded in Burrill's entry: *Mandatarius terminos sibi positos transgredi non potest* — a mandatary cannot exceed the limits assigned to him. This principle is substantively significant and appears across civil law jurisdictions as a limiting rule on agent authority. Researchers tracing the historical development of agent authority, scope-of-agency doctrine, or principal liability in mixed legal systems (particularly Louisiana, Quebec, or South African law) will find this maxim recurring as a foundational rule, sometimes cited in its Latin form without translation.
Researchers should be alert to the following traps:
First, the gratuitous nature of the mandate relationship distinguishes it from modern employment or commercial agency. The mandatarius acts without pay, which affects the standard of care owed — historically, a lower duty than that imposed on a compensated agent.
Second, the term will appear almost exclusively in sources drawing on Roman or continental civil law. Do not expect to find it in standard English common law digests, Blackstone, or American treatises in the common law tradition except as an explanatory gloss.
Third, in Louisiana legal materials — where civil law and common law coexist — *mandatarius* and *mandatory* appear in contexts directly traceable to French and Spanish colonial law antecedents. Corpus researchers working in Louisiana primary sources should note that the mandate relationship carries specific codified rules distinct from common law agency.
Historical Dictionary Support
Burrill's Law Dictionary provides the entry in its Latin form and correctly identifies the mandatarius as the civil law mandatary, citing the maxim from Jenk. Cent. 53 — referring to David Jenkins's *Centuries of Reports* (Jenkin's Centuries), a seventeenth-century collection of cases and maxims. Burrill's treatment is characteristically terse: it defines by reference to the anglicized equivalent and anchors the entry in the limiting maxim rather than expounding the relationship in full.
What Burrill does not address — and what researchers relying solely on this entry would miss — is the structure of the mandate relationship as a whole: the distinction between mandator and mandatarius, the requirement of gratuitousness, the question of what happens when a mandatarius acts in excess of authority (historically, the excess acts bind only the mandatarius personally, not the mandator), and the obligations running in both directions upon completion or abandonment of the mandate. For these, researchers must go beyond the dictionary entry to civilian treatises, Pothier's work on obligations, or the relevant provisions of civil codes in mixed jurisdictions.
No other historical dictionary in the current corpus covers this term. The absence is unsurprising — purely Latin-form civil law terms were more commonly treated in specialized civil law glossaries and Roman law commentaries than in general English legal dictionaries.
Jurisdictional Note
The concept mapped by *mandatarius* survives in codified form in Louisiana (Civil Code, Title on Mandate), Quebec, and other mixed or civil law jurisdictions. In pure common law jurisdictions, the functional equivalent is the gratuitous agent, governed by ordinary agency principles without the formal civil law terminology.