Definition
Latin. "By the rule of the common law." A phrase used in legal argument and judicial reasoning to signal that a result, rule, or obligation derives from the authority of the common law itself, as distinguished from a statute, equity principle, or local custom. The phrase operates as a sourcing marker: it identifies the legal basis for a conclusion without restating the rule in full.
Its companion phrase, per normam statuti ("by the rule of the statute"), performs the same function for statutory authority. The two phrases are most useful in contrast with each other — invoking one implicitly excludes the other as the operative source.
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Common Language
Neither Wiktionary nor Webster's 1913 contains entries for this phrase. It is pure Latin legal jargon with no meaningful common-language counterpart. Section omitted.
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Common Confusion
Per normam legis communis is sometimes loosely treated as synonymous with "at common law," but the phrases do different work. "At common law" describes a historical or baseline legal state — what the rule was before statutory modification. Per normam legis communis is more specifically an authority-attribution marker, asserting that the operative norm being applied comes from common law rather than any other source. A court might apply a common law rule to a modern fact pattern without using the phrase; conversely, the phrase appeared most naturally in contexts where the source of the rule was itself in dispute — particularly where a statute existed that might be thought to alter or displace the common law baseline.
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Why It Matters in Research
Researchers encountering this phrase in historical sources — especially pre-20th century English and American legal materials — should treat it as a flag that the source-of-authority question was live in the original dispute or argument. Its appearance often signals a brief, opinion, or treatise passage where the writer was distinguishing common law obligations from statutory ones, defending a result that a statute might seem to undercut, or arguing that a statute had not displaced an existing common law rule.
The phrase is most concentrated in materials dealing with tenure, real property, and obligations — areas where the interplay between ancient common law doctrine and successive waves of statutory reform was most contested. Bacon's reference in the Low's case of Tenures argument (cited by Burrill) is characteristic: tenure law was a domain where common law foundations coexisted uneasily with parliamentary modifications, making it essential to specify which norm governed.
Researchers using keyword searches should note that the phrase rarely appears in modern American case law. When it does appear in 19th-century American sources, it was typically borrowed from English practice and carries the same authority-signaling function. Its absence from a document does not mean the common law / statute distinction was not at issue — writers often conveyed the same idea in plainer English.
Per normam statuti, the companion phrase, should be searched alongside it. Arguments often pair the two explicitly or implicitly, and finding one frequently yields useful context about the other.
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Historical Dictionary Support
Burrill's Law Dictionary provides the only direct entry in the Law Mind shelf sources. Burrill's definition is characteristically concise: "By the rule of the common law," paired immediately with per normam statuti, "by the rule of the statute," and anchored to Bacon's argument in Low's case of Tenures (Works, iv. 242). That citation is significant. Francis Bacon's argumentative writings on tenure law were influential in both English and early American legal thought, and the pairing of the two normam phrases in that context confirms their function as tools of legal argument about competing sources of authority rather than as terms of art with fixed doctrinal content.
No other shelf sources in the current Law Mind corpus provide independent entries for this phrase. Its absence from American-origin dictionaries (such as Black's) reflects the progressive decline of Latin maxims in American practice through the 19th and 20th centuries. That absence should not be taken as evidence that the concept is obsolete — the underlying distinction between common law authority and statutory authority is fundamental and permanent; only the Latin label fell out of regular use.
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Jurisdictional Note
The phrase originates in English common law argument and appears primarily in English and early American materials. American courts largely abandoned Latin shorthand of this kind by the late 19th century, rendering the phrase a marker of historical rather than contemporary American practice. English and Commonwealth sources may preserve it longer in formal legal writing.
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