Definition
To wage law. In old English procedure, *legem vadiare* describes the act of offering or pledging to make a formal defense through the oath of the party and a prescribed number of compurgators — oath-helpers who swore to the truthfulness or credibility of the defendant's denial. The phrase is Latin for, roughly, "to wage" or "to pledge the law," and it denotes the initiation of the procedural mechanism known as wager of law (*vadium legis* or *lex*). When a defendant in a common law action — most commonly an action of debt or detinue — chose to wage law, he was offering to prove his case not through evidence but through solemn oath backed by compurgators, typically eleven in number, who swore in support of his oath.
The term functions as the verbal form of the broader procedural institution: wager of law is the institution; *legem vadiare* is the act of invoking it.
Common Confusion
*Legem vadiare* is sometimes loosely treated as synonymous with the completed process of wager of law (*lex*), but strictly it refers only to the offer or pledge to wage law — the initiating act — not to the performance of the oath itself. The completed procedure, once the compurgators actually swore, was the *lex* proper. The distinction matters in historical pleading records, where a defendant's failure to follow through after waging would carry different procedural consequences than a failure to wage in the first instance.
The term is also occasionally confused with *vadium*, the general concept of a pledge or gage, which had broader application beyond this procedural context.
Why It Matters in Research
This is a term of exclusively historical significance. No modern procedural system retains wager of law; Parliament abolished it in England in 1833 (Civil Procedure Act 1833, 3 & 4 Will. IV, c. 42). Researchers will encounter *legem vadiare* almost exclusively in:
— Medieval and early modern English plea rolls, Year Books, and abridgments, where it appears as a formulaic phrase in entries for debt and detinue actions.
— Treatises on common law pleading and practice predating the nineteenth century, particularly Glanvill, Bracton, and later Blackstone's *Commentaries* (Book III), which describe the procedure in its declining but still operative form.
— Historical scholarship on trial by oath and the transition from compurgation to jury trial.
The chief research trap is anachronism: applying modern evidentiary or procedural logic to records involving *legem vadiare*. The procedure was not a precursor to cross-examination or burden-of-proof analysis in any modern sense. It operated on entirely different assumptions about proof, credibility, and the social weight of sworn community testimony.
Corpus researchers should also note that the availability of wager of law was a significant tactical consideration in action selection. Plaintiffs who feared a defendant would successfully wage law often chose different forms of action — trespass on the case rather than debt, for example — specifically to foreclose that option. This strategic dimension appears prominently in the secondary literature on the evolution of common law forms of action and is a key thread connecting *legem vadiare* to the broader story of how assumpsit displaced debt.
Historical Dictionary Support
Black's Law Dictionary captures the core accurately: "to offer or to give pledge to make defense, by oath, with compurgators." This is a serviceable summary for identification purposes. The entry is thin, however, and does not situate the term within the procedural sequence (offer → formal waging → performance of oath → judgment) or flag the distinction between the pledge and the completed lex. Black's also does not note the strategic significance of the procedure or its eventual abolition.
Historical sources that go further include Blackstone's *Commentaries* and Glanvill's *Tractatus de Legibus*, where the mechanics of the oath and the role of compurgators are explained in operational detail. Maitland's historical writing on common law procedure provides the best modern synthesis of what *legem vadiare* meant in practice and why it fell into disfavor as courts and litigants found ways around it.
No historical dictionary source in the present corpus addresses the connection between *legem vadiare* and the transformation of the forms of action — a gap researchers should fill with secondary scholarship on legal history.
Jurisdictional Note
Wager of law, and therefore *legem vadiare*, was a feature of English common law and jurisdictions that derived their early procedure directly from it. It does not appear as a live procedural concept in American law, which had largely abandoned the form before or shortly after independence. Research into colonial American court records may surface the term, but its operational significance in that context varied by colony and period.
Encyclopedia Cross-Reference
See: WAGER OF LAW — for the full procedural institution, its elements, historical operation, and abolition.
See also: COMPURGATION — for the oath-helper system underlying this procedure.
See also: FORMS OF ACTION — for the strategic relationship between *legem vadiare* and the evolution of debt, detinue, and assumpsit.