Definition
In civil law, a constitutor is a person who, by simple agreement (without formal stipulation), undertakes personal responsibility for the payment of another's existing debt. The obligation assumed is a principal one — the constitutor is not a surety in the technical sense but a direct promisor who binds himself to satisfy a debt already owed by someone else. The instrument or agreement creating this arrangement is called a constitutum.
Common Language
Modern common usage (Wiktionary): One who or that which constitutes something — that is, a person or thing that establishes, creates, or makes up a whole.
Historical common usage (Webster's 1913): Not separately defined; derived from "constitute," meaning to set up, establish, or appoint.
The legal meaning is wholly unrelated to the common meaning. In ordinary English, a "constitutor" is simply something that constitutes or forms a larger thing. In civil law, the term is a precise technical label for a party to a specific debt-guarantee arrangement. A researcher encountering the word in a general text and a civil law source would be reading two entirely different concepts.
Common Confusion
CONSTITUTOR vs. SURETY vs. GUARANTOR: These three roles all involve secondary responsibility for another's debt, but they are legally distinct. A surety is bound alongside the principal debtor, typically by the same instrument, and is primarily liable. A guarantor is secondarily liable and can require the creditor to exhaust remedies against the principal first. A constitutor, in the civil law framework, promises by simple pact — without formal stipulation — to pay an already-existing debt. The obligation is principal in character (the constitutor cannot deflect to the original debtor as a first resort), but it arises informally, which is what distinguishes the constitutum arrangement from a stipulatio. Researchers applying common law guaranty concepts to civil law sources risk misreading the constitutor's liability posture.
Why It Matters in Research
CONSTITUTOR is a narrow term of art confined to the Roman and civil law tradition. It appears rarely in Anglo-American primary sources, but surfaces regularly in civil law treatises, Louisiana materials, Quebec sources, and in scholarly commentary on Roman law obligations. Researchers should be alert to three navigational points.
First, the term almost always appears alongside CONSTITUTUM. The two are inseparable: the constitutum is the agreement; the constitutor is the party making it. Sources that define one typically reference the other. Bouvier treats them as adjacent entries, and any corpus search for one term should include the other.
Second, the distinction between the constitutor's obligation and a stipulatio is historically important. A stipulatio required a formal oral exchange (later written formality); a constitutum required only a simple pact. In sources that predate or ignore Justinianic reforms, this procedural distinction carries weight for understanding what evidence of obligation would have been required.
Third, in American legal history, CONSTITUTOR has limited relevance outside Louisiana, where civil law continued after statehood. Researchers working in Louisiana historical records, notarial archives, or 19th-century Louisiana Supreme Court materials are more likely to encounter this term in operative legal documents than researchers focused on common law jurisdictions.
Historical Dictionary Support
All three source dictionaries are in close agreement. Black's (both editions) offers an identical, compressed definition: one who by simple agreement becomes responsible for another's debt. Bouvier adds the critical gloss that the obligation is "always a principal obligation" and that it must be for an existing debt — distinguishing the constitutum from a stipulation, which could relate to a future obligation.
Bouvier's entry is the most instructive, both for the term itself and because it flows directly into the CONSTITUTUM entry, making clear the relationship between the actor and the act. His citation to the Institutes (Inst. 4.6.9) is the foundational Roman law reference for this obligation type and points researchers toward the Justinianic source tradition.
What the historical dictionaries do not address: the practical evidentiary questions (what writings sufficed to prove a constitutum), the relationship between the constitutor and the original debtor after payment, and any right of subrogation or recourse. For those questions, treatise literature on Roman obligations and civil law commentaries are required.
Jurisdictional Note
CONSTITUTOR as a functional legal concept is operative primarily in civil law jurisdictions. In the United States, Louisiana is the most significant forum where this framework has historical relevance. Common law jurisdictions do not use the term, and the nearest functional equivalents — guaranty and suretyship — are governed by different doctrinal rules.
Encyclopedia Cross-Reference
See CONSTITUTUM (the agreement that gives rise to the constitutor's obligation; essential companion entry).