Definition
De fidee lasione is a Latin phrase meaning "of breach of faith" or "of breach of fidelity." It refers to an early common law action or ecclesiastical proceeding arising from a violation of pledged faith or trust — the breaking of a promise or oath that had been solemnly made. The term was used to describe causes of action, particularly in ecclesiastical courts, grounded not in a civil contractual wrong but in the moral and spiritual weight of a broken pledge.
---
Why It Matters in Research
Researchers working in early English legal history will encounter this term primarily in ecclesiastical court records and in historical surveys of the overlapping jurisdiction between church courts and common law courts in medieval and early modern England. The significance of de fidee lasione lies in the jurisdictional contest it represents: before the common law courts developed robust contract doctrine, the breach of a sworn oath was treated as a matter for ecclesiastical jurisdiction, enforceable on grounds of conscience and spiritual obligation rather than secular legal right.
A researcher tracing the development of contract law in England needs to understand that terms like this one represent an earlier conceptual world in which promise-breaking was simultaneously a legal wrong and a sin. The gradual displacement of ecclesiastical jurisdiction over breach of faith by common law assumpsit is a critical chapter in legal history, and de fidee lasione is a marker of the older regime.
The single Black's citation points to Reeve's History of English Law, a primary secondary source for this territory. Researchers should treat this as a prompt to consult Reeve directly rather than rely on Black's compressed treatment. The term will appear rarely in case law; its natural habitat is the treatise literature and ecclesiastical court records.
---
Historical Dictionary Support
Black's Law Dictionary (2nd Ed.) defines de fidee lasione as "of breach of faith or fidelity," with a sole citation to 4 Reeve, Eng. Law, 99. This entry is minimal — a phrase definition plus a single treatise pointer — and offers no procedural or jurisdictional elaboration.
The citation to John Reeve's History of English Law (a work from the late eighteenth and early nineteenth centuries) signals that the term's significance is historical rather than operative. Reeve's treatment in that volume addresses the ecclesiastical courts' claim to jurisdiction over cases involving breach of sworn faith, situating de fidee lasione within the broader story of how English courts divided subject matter jurisdiction in the medieval period.
Historical dictionaries are of limited help beyond this. The term does not appear to have generated a developed common law jurisprudence under its own name; rather, it describes a category of ecclesiastical proceeding that was either absorbed into or displaced by secular contract doctrine over time. Researchers should not expect to find this phrase deployed in reported cases as a cause of action in the modern sense.
---
Jurisdictional Note
This term belongs exclusively to English legal history and the history of ecclesiastical court jurisdiction in England. It has no operative meaning in modern American, English, or other common law jurisdictions. Researchers will encounter it only in historical sources addressing the medieval and early modern English legal system.
---