Nolo's Plain-English Law Dictionary

Ex Rel.

Abbreviation for Latin ex relatione, meaning "upon being related" or, more loosely, "on behalf of." The phrase is typically used in the title of a legal proceeding filed by the government, to indicate the name of an interested private party who pushed for the instigation of the suit. For example, a case caption might read: The State of Tennessee ex rel. Archie Johnson v. Hardy Products. Such suits usually happen when the private party's interests happen to coincide with those of the government or the public.
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