Definition
Calumnie jusjurandum (Latin: "oath against calumny") is a civil law procedural oath administered to both parties at the commencement of a suit, requiring them to swear that they were not acting with malicious or vexatious intent, but rather from a genuine and firm belief that their cause was just. The oath bound the plaintiff to swear that the suit was brought in good faith, not to harass or injure the opposing party; the defendant was equally bound to swear that the defense was raised in honest belief and not for purposes of obstruction or delay.
The oath had two components in practice: first, an affirmation of good-faith belief in one's own position; second, a renunciation of any intent to calumniate—that is, to pursue litigation as an instrument of malice rather than legitimate legal redress.
Why It Matters in Research
Researchers encounter this term almost exclusively in two contexts: comparative civil law scholarship and historical ecclesiastical or divorce proceedings. The oath was a creature of Roman and canon law and was transplanted into common law jurisdictions primarily through ecclesiastical courts handling matrimonial causes. Its appearance in American legal literature is therefore largely confined to pre-twentieth-century divorce treatises and to works on civil law procedure.
When tracing the oath in historical American sources, researchers should be alert to the overlap between calumnie jusjurandum and the broader procedural requirement of good-faith pleading. These are related but distinct: the oath was a formal, sworn act administered at the threshold of litigation, not merely an implicit professional obligation. Courts that absorbed canon law procedure—particularly in matrimonial jurisdiction—applied the oath in ways that common law courts did not.
The oath is of limited practical significance in modern American law, having been largely displaced by procedural rules requiring good-faith certification (such as Rule 11 of the Federal Rules of Civil Procedure), but its conceptual lineage connects directly to those modern requirements. Researchers working on the history of vexatious litigation doctrine or the evolution of sanctions for bad-faith pleading will find the oath a useful antecedent.
Bouvier notes that the oath was considered of "little practical utility" even within ecclesiastical divorce practice, a characterization that signals how weakly enforced it was in American jurisdictions that nominally recognized it. This should temper any inference that the oath functioned as a meaningful procedural gatekeeping device in practice.
Historical Dictionary Support
Black's and Bouvier's are in full agreement on substance. Both identify the oath as a civil law institution requiring litigants to affirm good faith at the commencement of suit. Bouvier adds useful detail: the oath was employed specifically to prevent vexatious and unnecessary litigation, and its most prominent American application was in divorce proceedings, where ecclesiastical law procedure had the strongest hold on domestic law courts.
Bouvier's citation to Bishop's treatise on marriage and divorce (Bishop, Marr. & Div. § 858) points researchers toward the most developed American treatment of the oath in domestic relations law. Black's reference to Justinian's Institutes (Inst. 4, 16) anchors the term firmly in Roman civil law and provides the classical source for comparative law inquiry.
Neither dictionary addresses the oath's treatment in Louisiana or other mixed civil law jurisdictions, where its survival or modification would be the most legally significant question. Researchers working in those jurisdictions should treat both entries as incomplete on that point.
Jurisdictional Note
The oath is essentially absent from modern American common law procedure. Its historical presence was most significant in ecclesiastical courts exercising matrimonial jurisdiction and in states whose procedural traditions incorporated canon or civil law elements. Louisiana, given its civil law heritage, is the jurisdiction most likely to preserve documentary traces of the oath's application in American practice.