Definition
TAVI (also rendered Tavi) is a historical designation for a supplemental collection of canon law promulgated by Pope Boniface VIII in 1298. The collection is more commonly known as the Liber Sextus Decretalium — the "Sixth Book of the Decretals" — so called because it was appended as a sixth book to the five-book Decretals of Gregory IX (the Liber Extra, 1234). The term TAVI itself is a shorthand label appearing in some legal reference works, derived from the opening words or classification conventions used in canonical bibliography, though the collection is far more frequently encountered under its Latin title.
The Liber Sextus was an authoritative compilation of papal constitutions and decretals issued between the close of Gregory IX's compilation and the pontificate of Boniface VIII. It was intended to update and supplement the existing Gregorian Decretals, resolving conflicts, filling gaps, and adding legislation generated over the intervening decades. The collection carried binding force throughout the Roman Catholic Church and shaped ecclesiastical jurisprudence well into the early modern period.
Why It Matters in Research
Researchers encountering TAVI in older legal texts — particularly in civil law treatises, ecclesiastical court records, or canonical commentaries — should treat it as a direct pointer to the Liber Sextus Decretalium. The abbreviation is uncommon outside of certain reference traditions and may appear without explanation in bibliographic footnotes or margin citations in early printed books. Confusion with other abbreviated canonical titles (Extravagantes, Clementinae, etc.) is possible for researchers unfamiliar with the structure of the Corpus Juris Canonici.
The practical research trap is this: the Liber Sextus was eventually incorporated into the Corpus Juris Canonici alongside the Decretum of Gratian, the Decretals of Gregory IX, the Clementinae, and the Extravagantes. A researcher working through civil law scholarship from the 12th through 19th centuries will encounter this layered structure constantly. TAVI as a label is a marker from a particular bibliographic tradition rather than a term of art in active canonical doctrine, so it will appear in secondary and tertiary sources (treatises, law dictionaries, bibliographic indexes) more often than in primary canonical texts themselves.
For Law Mind corpus researchers: this term surfaces in civil law foundations material and in entries touching ecclesiastical courts, marriage law, testamentary jurisdiction, and benefice disputes — all areas where canon law exercised concurrent or exclusive authority in many European jurisdictions prior to the Reformation and, in some regions, well after.
Historical Dictionary Support
Bouvier's Law Dictionary identifies TAVI as a supplemental canon law collection by Boniface VIII (1298), equating it with the Liber Sextus Decretalium, and cross-references Mackeldey's Civil Law (Kaufmann edition) for further bibliographic grounding. Bouvier's entry is brief and definitional, functioning primarily as a finding aid rather than a substantive doctrinal treatment.
Historical legal dictionaries generally treat this term as bibliographic shorthand rather than a legal concept requiring extended analysis. No significant doctrinal divergence exists among historical sources on its identity — the consensus is uniform that TAVI = Liber Sextus = the 1298 Bonifacian compilation. What historical sources do not address is the question of how to navigate the collection in research practice, which requires familiarity with the broader architecture of the Corpus Juris Canonici.
Jurisdictional Note
The Liber Sextus carried authority in ecclesiastical courts throughout the Latin Church. Following the Protestant Reformation, its operative jurisdiction contracted to jurisdictions remaining within Roman Catholic governance. In England, for example, canon law's reach was sharply curtailed after 1534, though ecclesiastical courts continued to apply portions of it in matters of marriage and probate until well into the 19th century.