Definition
A unit of liquid and dry capacity in the metric system, defined as one cubic decimetre (the cube of one-tenth of a metre). The historical legal dictionaries place the litre at 61.022–61.027 cubic inches, approximately 2.113 American liquid pints or 1.76 English pints — slightly more than a U.S. liquid quart. In legal contexts, the litre appears primarily in statutes and regulations governing weights and measures, trade, customs and excise, pharmaceutical standards, and commercial labeling requirements. It is a unit of measurement, not a legal concept in its own right, and its significance in legal sources is almost always definitional or regulatory rather than doctrinal.
Common Language
Modern common usage (Wiktionary): Alternative form of "liter" (the American English spelling).
Historical common usage (Webster's 1913): "Same as Liter" — a metric unit of capacity.
The common and legal meanings are essentially identical: the litre is a unit of measure in both ordinary and legal usage. The only meaningful gap for researchers is orthographic. American legal sources, statutes, and regulations overwhelmingly use the spelling "liter," while British Commonwealth jurisdictions, international treaty texts, and the International System of Units (SI) use "litre." Searching only one spelling in historical or international sources will produce incomplete results.
Why It Matters in Research
The primary research trap with this term is spelling variation. Pre-metric-adoption American statutes and case law rarely use either spelling; post-adoption federal and state statutes typically use "liter." British statutes, EU regulations, Canadian law, and international trade agreements use "litre." A researcher working across jurisdictions or time periods must run searches on both forms.
The numeric equivalents given in the historical dictionaries (61.022 vs. 61.027 cubic inches) reflect rounding differences in the underlying metrological standards of the era, not legal disagreement. Modern SI definition fixes the litre with greater precision; historical sources predating the 1964 redefinition of the litre may state slightly different equivalencies, which can matter in disputes over historical commercial contracts, customs valuations, or excise calculations.
In regulatory and commercial law research, the litre appears most often in: (1) weights and measures legislation and the regulations of standards bodies; (2) customs and tariff schedules, where volume measurements determine duty classifications; (3) food, drug, and alcohol labeling regulations; and (4) international trade contracts and carriage of goods documents. Researchers tracing the adoption of metric standards in a given jurisdiction should note that legal recognition of the litre as an official unit of commerce preceded its widespread practical use by decades in many common law countries.
Bouvier's cross-reference to MEASURE is the most useful pivot point in the historical dictionary corpus — the substantive law governing measurement units, conversion disputes, and trade standards is collected there rather than under individual unit headings.
Historical Dictionary Support
Black's Law Dictionary (1st and 2nd editions) carry identical entries, both citing Webster rather than a legal authority, signaling that the editors treated the litre as a factual and scientific term requiring definition for legal readers rather than a term with independent legal content. Bouvier's entry is marginally more precise in its geometric description (the cube of one-tenth of a metre) and gives a slightly different cubic-inch equivalent, reflecting the metrological reference each dictionary relied upon. None of the three historical sources discuss the legal status of the metric system, its adoption, or any controversy surrounding its use — the entries are purely definitional glosses.
Notably, all three historical dictionaries omit any discussion of the legal enforceability of metric measurements in commercial contracts, the regulatory history of metric adoption, or jurisdictional differences — gaps that are significant for any substantive research involving this term.
Jurisdictional Note
The United States recognizes both metric and customary units as lawful for commerce under federal law, but many labeling regulations require or permit metric units alongside customary equivalents. The United Kingdom completed statutory metrication of most trade measures by the early 2000s. Researchers working on pre-metrication British or Commonwealth sources will find the litre appearing rarely in older case law and more commonly in 20th-century regulatory materials.