Definition
*Enumeratio infirmat regulam in casibus non enumeratis.* A Latin maxim of statutory and legal construction meaning: "Enumeration weakens the rule in cases not enumerated." Where a legal instrument, statute, or rule expressly lists specific items, persons, or cases to which it applies, the act of enumeration implies that unlisted cases fall outside the rule's operation. The maxim captures the interpretive inference that a drafter who took care to name some things meant to exclude what was not named.
The maxim functions as a companion to — and partial inversion of — *expressio unius est exclusio alterius* (the expression of one thing excludes others). Where *expressio unius* focuses on the affirmative exclusionary force of a list, *enumeratio infirmat* focuses on the weakening of any general rule that the list purports to illustrate. Together they reinforce a single idea: specific enumeration signals deliberate choice, and deliberate choice implies deliberate omission.
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Common Confusion
ENUMERATIO INFIRMAT is frequently conflated with *expressio unius est exclusio alterius*, and the two maxims are sometimes cited interchangeably. The distinction, though subtle, matters for research. *Expressio unius* operates primarily as an exclusionary rule — naming A excludes B. *Enumeratio infirmat* operates as a limiting rule on generality — a general proposition followed by specific examples is narrowed to those examples, and the general rule does not reach unenumerated cases. In practice, courts sometimes deploy one maxim where the other would be technically more precise. Researchers should check both when working through a canon-of-construction problem.
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Why It Matters in Research
This is a maxim of legal construction, not a freestanding doctrine, which means it surfaces in case law as interpretive reasoning rather than as a named legal rule. Several research traps follow from that character.
First, the full Latin phrase varies in truncation across historical sources. Black's 2nd Edition records the phrase cut short — the fragment "Enumeratio infirmat regulam in casibus" appears without completing "non enumeratis." Researchers encountering partial quotations in older opinions or treatises should recognize this as the same maxim and reconstruct the full form.
Second, the maxim is most heavily invoked in three clusters of legal material: (1) constitutional law cases addressing the scope of enumerated governmental powers, particularly the enumerated powers of Congress and the interpretive question of what follows from their express listing; (2) tariff and customs classification disputes, where the presence of specific schedules was argued to limit the reach of general catch-all provisions; and (3) property and testamentary instruments, where specific enumeration of items or beneficiaries was used to argue against implied inclusion of omitted items. The Black's 2nd Edition entry gestures at all three with its citation pattern.
Third, because this is a maxim rather than a rule, courts have treated it as rebuttable by contrary evidence of intent. A researcher who finds the maxim cited in one opinion in a line of cases should not assume it controlled the outcome — subsequent decisions in the same line may have declined to apply it where context indicated the enumeration was illustrative rather than exhaustive.
Fourth, the maxim appears almost entirely in pre-twentieth-century American legal writing and in courts engaging with classical common-law construction methodology. Modern statutory interpretation scholarship and federal courts influenced by textualism tend to absorb this maxim into the broader *expressio unius* canon without separate treatment. Researchers working in post-New Deal federal administrative law may find it largely invisible as a named maxim even where its logic is operative.
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Historical Dictionary Support
Black's Law Dictionary (2nd Edition) is the primary dictionary source here, and its treatment is fragmentary — the entry appears as a subentry under "ENUMERATED," where it is cut off mid-phrase. The surrounding context in that entry defines "enumerated" as "specifically," "designated," or "expressly named or granted," illustrated by references to enumerated governmental powers, items of property, and tariff schedules. The truncation of the maxim in Black's 2nd is itself a research artifact worth noting: it reflects the maxim's role as supporting material for the concept of enumeration generally, rather than as a standalone doctrine warranting its own full entry.
No dedicated entry for the full maxim appears in the available historical dictionary sources beyond this fragment. This is consistent with the maxim's character as standard Latin brocard — the kind of construct that nineteenth-century legal writers assumed trained readers would complete from memory.
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Jurisdictional Note
The maxim is general to common-law jurisdictions and carries no jurisdiction-specific variant. Its weight in any given court depends on how that court treats Latin maxims and canons of construction generally — federal courts and state courts with strong textualist traditions have largely absorbed it into *expressio unius* analysis without separate citation.
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