Definition
Irregularitas (also rendered "irregularity" in English) is a term drawn from medieval Latin legal usage, denoting a formal defect, departure from prescribed procedure, or breach of canonical or legal rule that renders an act, proceeding, or person subject to censure, disqualification, or nullity. In its historical English legal context, the term appears most prominently in ecclesiastical and canon law, where it described a canonical impediment — a personal defect or disqualifying circumstance — that barred a person from receiving holy orders or exercising ordained functions. By extension, the term was applied in common law practice to any procedural irregularity: a departure from established forms that, depending on its gravity, could void a proceeding or merely subject it to challenge.
The scope of the term in older usage was broader than the modern English "irregularity" suggests. Bracton and other medieval jurists applied irregularitas to persons as well as to proceedings — a usage that later contracted in English common law to refer almost exclusively to defects in procedure or process rather than to personal disqualifications.
Common Confusion
Irregularitas should not be conflated with nullity or with voidness generally. An irregularity, in both historical and modern procedural usage, is typically a curable defect — one that may be waived, corrected, or excused — whereas a nullity renders an act void from the outset and beyond ratification. The distinction matters in research: sources that use irregularitas may be describing a remediable departure from form, not an absolute legal incapacity. In canon law, the distinction between an irregularitas (personal impediment) and a mere inhabilitas (incapacity) further complicates interpretation of medieval ecclesiastical sources.
Why It Matters in Research
Researchers encountering irregularitas in primary sources face two distinct interpretive challenges depending on the body of law at issue.
In canonical and ecclesiastical sources, irregularitas is a term of art with a developed technical meaning: a permanent or semi-permanent personal impediment preventing ordination or the exercise of orders. Sources in this tradition — church councils, papal decretals, commentaries on the Decretum or Decretales — use the term with precision. A researcher reading these materials through the lens of common law procedural usage will misread them entirely.
In English common law sources — particularly Bracton and the medieval Year Books — the term bridges the canonical and procedural senses. Bracton's usage (fol. 407, cited in Burrill) reflects the still-unified medieval legal culture in which ecclesiastical and secular courts shared conceptual vocabulary. By the time of Coke and the later common lawyers, the term had largely been anglicized to "irregularity" and narrowed to its procedural sense.
The Burrill note that older usage extended to persons as well as property is an important flag: do not assume that an irregularitas reference in pre-modern English sources is exclusively procedural. The canonical personal-impediment sense may be operative, particularly in any matter touching on clerical status, ordination, or ecclesiastical office.
Modern civil procedure uses "irregularity" frequently, but the Latin form irregularitas is a signal that the source is medieval or early modern and that canonical context should be considered before applying a contemporary procedural gloss.
Historical Dictionary Support
Burrill's Law Dictionary provides the core entry: a Latin form meaning "irregularity" in old English law, with the illustrative phrase "ne committat irregularitatem" (lest he be guilty of irregularity) drawn from Bracton, fol. 407. Burrill appends the significant note that in older usage the term extended to persons as well as property, though modern law confined it to the latter — a compressed observation that contains an important historical signal about the term's semantic contraction over time.
The Bracton citation grounds the term firmly in thirteenth-century English legal usage, at a period when English common law was still heavily inflected by civilian and canonical learning. Bracton's treatise is the primary English-language repository of this hybrid medieval legal vocabulary.
Historical dictionaries beyond Burrill (Cowell, Blount, Jacob, Tomlin) address "irregularity" in its anglicized procedural sense but do not typically treat irregularitas as a discrete entry, reflecting the term's absorption into English usage by the early modern period.
Jurisdictional Note
In canon law, irregularitas retains technical force in ecclesiastical legal systems derived from Roman Catholic canon law, where it continues to designate personal impediments to ordination. Common law jurisdictions absorbed the term into general procedural vocabulary as "irregularity," and the Latin form is now encountered only in historical sources and ecclesiastical contexts.