Definition
Ex relatione (abbreviated ex rel.) is a Latin phrase meaning "upon the relation of" or "on the information of." It identifies the private individual — called the relator — at whose instigation and for whose benefit a legal proceeding is brought, even though the action is formally prosecuted in the name of the state or a public officer.
In practice, when a state attorney general, prosecutor, or other authorized officer brings suit in an official capacity but does so at the request of a private party who has a direct interest in the outcome, the private party's name appears in the case caption following the abbreviation ex rel. A typical caption reads: State ex rel. [Private Party] v. [Defendant]. The action is the state's in name; the driving interest is the relator's in fact.
The phrase also appears in legal writing and reported opinions to signal that information was received by relay — that is, the reporting attorney or judge learned the facts not firsthand but through a third party's account. In this secondary usage, ex relatione functions as an attribution marker, equivalent to "as reported by" or "on the information of," and is sometimes abbreviated ex rel. amici.
Common Confusion
Ex relatione is frequently confused with ex parte, and the confusion is understandable: both involve a proceeding where not all interested parties appear on the same footing. The distinction is structural. An ex parte proceeding involves only one side — the opposing party is absent altogether. An ex rel. action involves a private relator who rides behind a public officer's authority; all parties are present, but the caption masks who is actually driving the litigation. The two Latin phrases describe different procedural asymmetries.
Ex rel. is also sometimes misread as shorthand for ex relatione amici (on the information of a friend), a usage appearing in older reported decisions where a case was transmitted through an intermediary. Context — specifically whether a case caption or a citation is involved — determines which usage applies.
Why It Matters in Research
Case caption reading is the most immediate practical concern. Searching historical reporters for a party's name may fail entirely if that name appears only after ex rel. in the caption. Early American reporters were inconsistent about indexing relators; some indexed under the state's name, others under the relator's, and many did neither reliably. Researchers hunting a specific dispute should search both the official party name and the relator's name.
The ex rel. form was the standard vehicle for quo warranto and mandamus actions through the nineteenth and early twentieth centuries, when private citizens had no direct right of action to challenge official conduct and had to proceed through the attorney general as a nominal plaintiff. Understanding this procedural architecture is essential for reading those cases correctly: the "state" suing is often a fiction, and the real legal theory and interest belong to the named relator.
Modern qui tam actions under the False Claims Act follow an analogous structure — a private relator brings suit in the government's name and shares in any recovery — though qui tam has its own statutory vocabulary and is not typically captioned ex rel. in the traditional sense. Researchers moving between historical ex rel. actions and modern qui tam litigation should note the family resemblance without assuming identical procedural rules apply.
In secondary literature and older treatises, the attribution use of ex relatione (meaning "as reported by") appears without any connection to relator practice. Burrill cites Bracton for this usage, placing it deep in the common law tradition of oral relay reporting. When encountered in a treatise footnote rather than a case caption, ex rel. signals evidentiary provenance, not party structure.
Historical Dictionary Support
The historical dictionaries converge on the core meaning without meaningful divergence. Black's (both editions) emphasizes the procedural function — the attorney general acting at a private party's instigation — and provides the caption structure that remains recognizable today. Burrill traces the phrase to Bracton, confirming its deep roots in medieval common law practice and its original function as an attribution marker. Rapalje & Lawrence note the ex rel. amici usage in reported decisions, which is the secondary attribution sense Burrill identifies.
What the historical dictionaries do not address is the evolution of standing doctrine that gradually made the ex rel. form less necessary. As courts developed direct private rights of action and as administrative law expanded, the procedural necessity of routing private claims through a public officer diminished. The dictionaries capture the form at its height; they do not track its partial displacement. Researchers working in twentieth-century materials should be alert to this transition.
Jurisdictional Note
While the ex rel. caption form is recognized across American jurisdictions, the procedural rules governing when a private party may compel an attorney general to lend the state's name vary significantly by state. Some states grant the attorney general broad discretion to refuse; others have statutory relator procedures that constrain that discretion. Federal practice has its own distinct ex rel. conventions, particularly under the False Claims Act.
Encyclopedia Cross-Reference
Constitutional Law Encyclopedia: Ex parte Young — The Fiction That Permits Suits Against State Officers (constitutional_42) — relevant for understanding how courts use nominal-party fictions to manage sovereign immunity, a structural parallel to ex rel. practice.