Definition
In Roman law, *patrocinium* referred to the relationship of patronage, protection, and defense that a *patronus* (patron or advocate) owed to those under his care. The term carried two closely related but distinct meanings in Roman legal usage:
1. The social and legal bond between a patron and his clients or freedmen — a structured relationship of obligation, protection, and loyalty that permeated Roman civic life.
2. The professional duty and function of an advocate before a Roman court or tribunal — the work of speaking, defending, and representing another in legal proceedings.
These meanings were not entirely separate. The advocate's role in court was understood as an extension of the broader patron-client relationship: to defend someone was to protect them, and protection was the defining obligation of the *patronus*. The term thus captures both the social institution and its legal expression in courtroom advocacy.
Common Language
Modern common usage (Wiktionary): The distinctive relationship in Ancient Roman society between a patron and a client.
The common usage captures the social dimension of the term but leaves out its legal and forensic meaning. In legal sources, *patrocinium* is not merely descriptive of a social arrangement — it is a term of art pointing specifically to the duties and obligations that flowed from the patron-client bond, including the obligation to provide legal defense. Researchers working in Roman law sources will encounter the term in advocacy contexts where the social relationship is largely in the background.
Why It Matters in Research
*Patrocinium* is a Latin term appearing in Roman law sources, civil law commentaries, and early common law treatises that drew on Roman legal foundations. Researchers are most likely to encounter it in:
— **Civil law jurisdictions and their historical sources**: Louisiana, Quebec, and other mixed jurisdictions with civil law heritage inherited Roman terminology through French and Spanish intermediaries. *Patrocinium* may appear in foundational texts without English translation.
— **Treatises on Roman and canon law**: Works such as Justinian's Digest (*Digesta*) and Institutes, and the commentaries of Civilian scholars, use *patrocinium* as a term of legal art. Researchers consulting these sources directly, or early English treatises that borrowed from them, should understand that the term encompasses both the social bond and the professional advocacy duty.
— **Early common law sources**: English legal writers of the sixteenth and seventeenth centuries, drawing on Roman models, occasionally used *patrocinium* and related Latin terminology in discussions of the barrister's role and obligations to clients. The term is not a native common law concept, but its influence on thinking about professional duty and client loyalty should not be dismissed.
— **Transitional meaning risk**: A researcher reading a historical source that uses *patrocinium* must determine from context whether the author means the general social institution of patronage, the specific professional function of advocacy, or both. The term was often used loosely in secondary sources, and collapsing the distinction can distort the analysis.
The connection to *patronus* is indispensable for navigating this term across sources. *Patrocinium* is essentially the abstract noun form of what a *patronus* does.
Historical Dictionary Support
Black's Law Dictionary and Burrill's Law Dictionary are in complete agreement on this term, and their definitions are nearly identical: patronage, protection, defense, and the business or duty of a patron or advocate. This convergence reflects that *patrocinium* had a settled meaning in the Roman law tradition by the time these dictionaries were compiled in the nineteenth century, and there was little occasion for interpretive dispute.
Neither source attempts to distinguish the social-institutional dimension from the forensic-advocacy dimension, treating both as subsumed under the single definition. This is accurate as far as it goes, but researchers should be aware that classical Roman sources and later civil law commentators sometimes used the term with greater precision. Burrill's cross-reference to *Patronus* is the more useful pointer for further research, as that entry develops the patron-client relationship more fully.
Neither dictionary traces the term's passage into early modern civil law commentary or its relevance to the professional ethics of advocacy — a gap that researchers approaching this term from a legal history or comparative law angle will need to fill from primary sources.
Jurisdictional Note
*Patrocinium* as a term of art is a Roman and civil law concept with no direct counterpart in common law terminology. Its practical significance today is greatest in jurisdictions with civil law heritage and in academic legal history. It does not appear as a operative legal term in modern American or English statutes or case law.