Definition
An old Law French term meaning to turn aside or divert from its course. Used in early English legal practice to describe the diversion or deflection of something — most commonly a watercourse or stream — from its natural or accustomed path. The term appears in medieval and early modern pleading and real property contexts, where the wrongful diversion of water was a recognized legal injury giving rise to action.
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Common Confusion
TRESTOURNER should not be confused with general terms of obstruction or stoppage. The word carries the specific sense of turning aside — a lateral diversion — rather than blocking, damming, or destroying entirely. Burrill's entry illustrates this with the phrase *ewe trestourne*, meaning a stream diverted, suggesting the operative harm is redirection rather than cessation.
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Why It Matters in Research
This term is essentially a relic of Law French pleading and will appear almost exclusively in pre-modern English legal records — year books, plea rolls, and early treatise literature — rather than in reported case law from the nineteenth century onward. Researchers working in manuscript sources, early printed abridgments, or antiquarian treatises on riparian rights and water law may encounter it without ready glossaries nearby.
The surviving Burrill entry is fragmentary. The text breaks off mid-phrase — *"actissima litis contestatæ, coram judice, per VOL. II"* — indicating a printing or transcription artifact rather than a complete definition. This is a known hazard in digitized versions of older multi-volume dictionaries: volume and page references embedded in the typeset original sometimes bleed into the definitional text during reproduction. Researchers relying on digital versions of Burrill should verify against the original print edition when precision matters.
The underlying concept — the wrongful diversion of a watercourse — connects to a broad and durable body of riparian law that persisted long after the Law French vocabulary was abandoned. Later English and American cases address the same injury under terms like *diversion of a watercourse*, *interference with riparian rights*, or actions on the case for nuisance. A researcher who encounters *trestourner* in a historical source and needs to trace the doctrine forward should shift to those modern designations.
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Historical Dictionary Support
Burrill's Law Dictionary is the primary English-language legal dictionary source for this term. Burrill defines it succinctly as "[t]o turn aside or divert from its course," offering *ewe trestourne* — a diverted stream — as the illustrative phrase. No substantive definition appears in Jacob's Law Dictionary, Tomlin's Law Dictionary, or Black's Law Dictionary, which suggests the term had fallen out of active use well before the nineteenth-century lexicographers were writing for practicing audiences.
The incompleteness of the Burrill entry is notable. What survives reads like an editorial cross-reference that was improperly folded into the definition itself — the phrase beginning *actissima litis contestatæ, coram judice* (Latin for "in the heat of the contested suit, before the judge") appears to be a fragment of a separate citation or illustrative passage rather than a continuation of the definition. Researchers should treat the Burrill entry as confirming the term's meaning and general context while remaining alert to the possibility that the full entry contained additional contextual detail now obscured by transcription error.
No common-usage counterpart exists in standard English dictionaries. The term is pure Law French legal vocabulary with no parallel life in ordinary language.
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Jurisdictional Note
TRESTOURNER is a term of English legal origin with no independent development in American, Scottish, or continental legal systems. It is relevant only in research touching early English common law, and its functional successor doctrine — riparian rights and watercourse diversion — developed differently in England versus the American prior appropriation states of the West.
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