Definition
Decretalium (also rendered Decretalia or, in its familiar abbreviated Latin genitive form, Decretalium) refers to the body of papal decretals — authoritative letters and rulings issued by popes in response to specific legal or ecclesiastical questions — compiled into formal collections that served as primary sources of medieval canon law. The term is most commonly encountered in legal research as a reference to the Liber Extra (officially Decretalium Gregorii Papae IX Compilatio), compiled by Raymond of Peñafort and promulgated by Pope Gregory IX in 1234, which became the foundational decretal collection of the Western Church. In broader usage, "the Decretals" or "Decretalium" may refer collectively to the several official collections of canon law texts that succeeded Gratian's Decretum, including the Liber Sextus (1298) of Boniface VIII, the Clementinae (1317), and the Extravagantes.
As a corpus, the Decretalium functioned as operative law across ecclesiastical courts throughout Catholic Europe for several centuries, governing matters including marriage, inheritance, clerical discipline, testamentary succession, and the relationship between church and secular authority.
Why It Matters in Research
The primary research trap with this term is its shifting referent. In older English and American legal sources, "the Decretals" or "Decretalium" may refer narrowly to Gregory IX's 1234 compilation, to the Corpus Juris Canonici as a whole, or loosely to any body of papal legislative pronouncements. A researcher encountering the term in a 17th- or 18th-century common law treatise must determine which layer of the canon law corpus is actually meant before drawing conclusions about applicable doctrine.
The entry in Rapalje & Lawrence is notably sparse — identifying Decretalium only as "the sixth decretal" and cross-referencing Canon Law — which reflects the treatment of the term as a pointer rather than a substantive entry in most Anglo-American legal dictionaries. This is characteristic of the period: common law compilers treated canon law sources as reference material for specific doctrinal domains (ecclesiastical jurisdiction, marriage validity, probate) rather than as living law requiring full exposition.
Researchers working in pre-Reformation English law, colonial American ecclesiastical matters, or the history of marriage and probate law will encounter the Decretalium as operative authority. Post-Reformation English sources, particularly after the break with Rome, reference the Decretals with increasing skepticism or hostility, and some authorities deny their force in English courts entirely — a shift that must be tracked when reading cases from Tudor period onward.
In the Law Mind corpus, this term connects most directly to Canon Law materials and to entries touching ecclesiastical jurisdiction, marriage, and testamentary law. Researchers tracing doctrines that migrated from canon law into equity or common law (such as constructive fraud, consideration in contracts of a quasi-spiritual nature, or the law of wills) may find the Decretalium cited as an ancestral source even in secular legal texts.
Historical Dictionary Support
Rapalje & Lawrence offer only a minimal entry, describing Decretalium as "the sixth decretal" and directing readers to Canon Law. This truncated treatment is common in Anglo-American legal dictionaries, which generally treated the canon law corpus as background rather than foreground. The cross-reference to Canon Law suggests the compilers understood the term as part of a larger system requiring fuller treatment elsewhere rather than as a standalone concept demanding independent exposition.
Historical civilian and ecclesiastical dictionaries provide considerably richer treatment. The standard account — consistent across continental sources — identifies the Decretalium with the Gregorian compilation of 1234, distinguishing it from the earlier Decretum of Gratian (which was not a collection of papal letters but a systematic reconciliation of conflicting canons). The Liber Sextus of Boniface VIII was so named because it was intended as a sixth book supplementing Gregory's five-book compilation, a naming convention that explains why Rapalje & Lawrence's brief entry characterizes the term as referencing "the sixth decretal."
What the historical Anglo-American dictionaries largely omit is any account of how the Decretalium functioned procedurally — its role in ecclesiastical courts, its influence on the development of equity jurisdiction, and the extent to which English ecclesiastical lawyers continued to cite it after the Reformation through the survival of the Court of Arches and other church courts.
Jurisdictional Note
The Decretalium carried operative legal force in Catholic jurisdictions throughout medieval and early modern Europe. In England, its authority was progressively curtailed following the Reformation and the Henrician supremacy statutes, though ecclesiastical courts continued to apply canon law in marriage and probate matters. In the United States, the Decretalium has no direct operative force but may appear as a historical source in tracing the origins of doctrines absorbed into common law or equity.