Definition
Mensura Domini Regis (Latin: "the measure of our lord the king") is the royal standard of weights and measures established under King Richard I at the Parliament of Westminster in 1197. It represented the Crown's assertion of authority to set uniform commercial and civic measures across the realm, making the king — rather than local lords or merchants — the source of standardized units used in trade and governance. Also rendered as mensura regalis ("the royal measure"), it denoted the official standard kept in the royal exchequer against which other weights and measures were to be calibrated.
Why It Matters in Research
This is a term of medieval English constitutional and commercial history, not a term appearing in modern statutory or common law. Researchers will encounter it almost exclusively in historical legal texts, particularly those addressing the development of English weights and measures law, the prerogatives of the Crown, or early parliamentary history.
Several navigational points merit attention:
First, the 1197 date anchors the term to a specific constitutional moment. Researchers tracing the history of standardization should connect it to Magna Carta (1215), which in Chapter 35 addressed uniform weights and measures across England — a provision directly continuous with the mensura Domini Regis tradition. The 1197 Parliament is a precursor event in that lineage.
Second, Burrill's entry conflates or juxtaposes this term with "MENEE" or "Meyne," a distinct Anglo-French term meaning a leading or retinue, and fragments of a separate discussion of hue and cry. This is an editorial artifact of Burrill's compilation method and should not mislead researchers into treating mensura Domini Regis as connected to hue and cry or the law of pursuit. The entries are separate concepts that appear to have been run together in Burrill's text.
Third, Blackstone's Commentaries (1 Bl. Comm. 275–276) is the primary secondary source for this term in the historical dictionaries. Researchers seeking deeper treatment should go to Blackstone directly rather than relying on the dictionary glosses, which are thin. Fleta, a late 13th-century legal treatise cited by Burrill (lib. 2, c. 12), provides an earlier primary source reference.
Fourth, the term has no modern legal relevance in practice but may surface in property, commercial, or constitutional history scholarship — particularly work on the prerogative powers of the English Crown or the origins of parliamentary regulation of trade.
Historical Dictionary Support
Black's and Bouvier's entries are nearly identical and both trace directly to 1 Blackstone's Commentaries 275, offering no independent analysis. Neither adds to the other.
Burrill's entry is the most textually interesting but also the most editorially unreliable for this term. Burrill references Fleta (lib. 2, c. 12) as a primary source and notes the alternative name mensura regalis, both useful additions. However, Burrill's entry then immediately transitions — apparently without clean separation — into a discussion of "MENEE" or "Meyne" and hue and cry, citing Britton (c. 12, 27) and Cowell. This creates genuine confusion in the source text itself. The editorial note in Burrill referencing the standard measure "kept in the exchequer" is consistent with historical practice: a physical exemplar was maintained as the authoritative reference against which local measures were tested.
Mozley & Whitley (cited by Black's) is a 19th-century legal dictionary that treats this as a minor historical gloss, consistent with its treatment in Black's.
None of the three source dictionaries situate mensura Domini Regis within the broader history of weights and measures legislation or trace its relationship to Magna Carta, leaving that connective work to the researcher.
Jurisdictional Note
Exclusively English in origin and application. The term has no direct counterpart or reception in American law, though the U.S. constitutional grant to Congress of power to "fix the Standard of Weights and Measures" (Art. I, § 8, cl. 5) reflects a conceptually parallel sovereign function. Researchers working in early American legal history may find the English antecedents useful for comparative framing but should not expect the Latin term itself to appear in American sources.
Encyclopedia Cross-Reference
See Law Mind Encyclopedia: Weights and Measures (Historical); Crown Prerogative; Magna Carta and Commercial Regulation.