Definition
In Roman law, an adstipulator was a secondary party to a formal promise (stipulatio) who received the same promise made to the principal creditor and held independent authority to enforce or collect on that promise. The adstipulator stood alongside the principal stipulator rather than beneath him — not a mere witness or agent, but a co-promisee with his own enforceable claim. His rights could be coextensive with the full promise or, when he stipulated only for a part, limited to that lesser amount. If the adstipulator collected payment, he was obligated to account to the principal; a failure to do so gave rise to an action under the lex Aquilia.
The institution served a practical function in Roman transactional life: because a stipulatio was strictly personal and died with the promisee, an adstipulator allowed the promisee to arrange for collection after death by having a living co-promisee who could act.
Common Confusion
The adstipulator is easily confused with the adpromissor (or adpromitor), who occupied the opposite position in a Roman transaction — standing beside the debtor as a surety or guarantor of performance, rather than beside the creditor as a co-promisee. The two terms are structural mirrors: the adpromissor reinforces the obligation from the debtor's side; the adstipulator reinforces the claim from the creditor's side. Conflating them reverses the entire legal relationship. Researchers encountering either term in Roman law sources or civil law commentaries should fix the party's position in the transaction before drawing any analogy to modern doctrine.
Why It Matters in Research
This is a term of pure Roman law with no surviving direct counterpart in common law doctrine. Researchers will encounter it almost exclusively in three contexts: (1) treatises and institutional works on Roman law cited within Anglo-American legal dictionaries, particularly works in the Justinian tradition; (2) historical civil law scholarship and comparative law writing where Roman obligatory structures are mapped onto later civilian systems; and (3) early English equity and contract theory, where Roman concepts occasionally surfaced in scholarly argument without being formally adopted.
The key navigational point is that adstipulator is a dead-end for common law research — finding the term in a 19th-century American or English legal dictionary tells you that the editor drew on Roman sources for completeness, not that the concept had operative legal force in that jurisdiction. Do not treat its appearance in Black's as evidence of common law recognition.
For researchers working in civil law jurisdictions or comparative private law, the adstipulator connects to broader questions about how Roman stipulatio shaped modern contract theory, particularly the enforceability of third-party claims and assignment of contractual rights — areas where Roman law's strict personal character created problems that later civilian systems resolved differently.
The Sandars citation (Justinian's Institutes, 5th Ed.) referenced in both Black's editions is a real and reliable secondary source for Roman law context. Thomas Collett Sandars's annotated edition of the Institutes was a standard English-language reference for Roman law in the 19th century and remains a legitimate historical source.
Historical Dictionary Support
Both the first and second editions of Black's Law Dictionary carry identical substantive definitions, differing only in a minor typographical artifact in the second edition (a corrupted citation string rendering "5th Ed." as "@®th Ed." — a printing error, not a different source). Both trace directly to Sandars's Justinian's Institutes. Neither edition elaborates beyond the structural description or provides any English case authority, which itself signals the term's purely doctrinal-historical character.
What the historical dictionaries do not address: the procedural mechanism by which an adstipulator's claim was extinguished upon collection, the lex Aquilia liability for misappropriation, or the relationship between the adstipulator institution and the Roman prohibition on stipulating for another's benefit (alteri stipulari nemo potest). Researchers needing the full Roman law picture must go beyond Black's to the Institutes themselves (Book III) or to Gaius's Institutes, which treat the subject with greater analytical depth.
Jurisdictional Note
Adstipulator is a Roman law term with no operative jurisdiction in any common law system. It retains relevance in academic civil law contexts and in Louisiana, Quebec, and other mixed jurisdictions where Roman law concepts inform scholarly analysis of obligatory relations, but it has not been adopted as a term of positive law in any modern American or English jurisdiction.