Definition
Customs has two primary legal meanings that are related by origin but function differently in legal research:
1. Import/Export Duties. The taxes, duties, tolls, or tariff charges levied by a government on goods and merchandise crossing an international border — whether imported into or exported from the country. The revenue collected through these charges forms a distinct stream of public finance administered by a dedicated government agency.
2. The Government Agency. The administrative body authorized to assess, collect, and enforce duties on imported and exported goods, and to control the flow of merchandise across national borders. In the United States, this function is carried out by U.S. Customs and Border Protection (CBP), a component of the Department of Homeland Security.
A third, older legal meaning — "custom" in the singular or plural as an unwritten rule of practice acquiring the force of law through long usage — is distinct from customs in the fiscal sense and is treated separately. See RELATED TERMS.
Common Language
Modern common usage (Wiktionary): The duties or taxes imposed on imported or exported goods; the government department authorized to collect those taxes; the process of going through customs checks at a border checkpoint; and the physical location at a border where those checks occur.
Historical common usage (Webster's 1913): A toll or tax levied on goods imported or exported; habitual practice; common usage or tradition.
The legal meaning of customs (fiscal) aligns closely with the common meaning as applied to duties and the agency. The risk for researchers is conflation with the separate legal concept of "custom" as an unwritten rule of law — a usage that appears throughout early common law sources and that shares the same ordinary-language root but operates on entirely different legal principles.
Common Confusion
Customs (fiscal duties and the enforcing agency) must be distinguished from custom or customary law — the doctrine by which long-established, consistent local practice acquires legal force equivalent to enacted law. Both terms appear in historical legal sources, sometimes on the same page. Burrill and Bouvier both carry entries treating the fiscal and customary-law senses, and older law Latin sources use custuma for duties and consuetudines for practices/usages — a distinction Blackstone preserves explicitly. When reading pre-twentieth-century sources, confirm which sense is intended before applying authority.
Recognized Forms
/SUBTYPES
Ancient Customs (Antiqua Custuma): In English legal history, the original duties on wool, wool-fells, and leather, imposed by Edward I and predating parliamentary grants of additional duties. Distinguished in historical sources from Nova Custuma (new customs) imposed on foreign merchants.
Nova Custuma (New Customs): Additional duties on merchandise beyond the ancient customs, often imposed by royal prerogative and later subject to parliamentary challenge. Anderson's Dictionary traces the crown's historical claim to customs as "almost immemorial" revenue.
Ad Valorem Duties: Customs calculated as a percentage of the declared value of imported goods — as opposed to specific duties assessed at a fixed rate per unit regardless of value.
Why It Matters in Research
Researchers working in U.S. constitutional law will encounter customs primarily through Article I, Section 8 (the taxing and commerce powers) and Article I, Section 9 (the uniformity requirement for duties). The Pollock v. Farmers' Loan & Trust Co. line of cases, referenced in Black's 2nd Ed., connects customs to broader debates about federal taxing power in the late nineteenth century.
Historical sources use customs interchangeably with duties, imposts, and tariffs in ways that modern usage has partly separated. Impost was favored in constitutional debates to refer to import duties specifically; tariff became the dominant political term in the nineteenth century; customs has remained the administrative and statutory term of art. Treat these as substantially overlapping but not identical when tracing legislative history.
In English legal history, customs revenue was a source of significant constitutional conflict — the crown's claim to levy customs by prerogative (without parliamentary consent) was contested across centuries. Sources from Coke forward reflect this tension. Anderson's Dictionary notes customs were "exactions maintained by the crown" before parliamentary control was established. This history is invisible in modern U.S. administrative law research but essential for reading English common law sources.
For researchers using the Law Mind corpus on international trade, export controls, or border enforcement, the agency meaning of customs is dominant. For researchers in constitutional history, revenue law, or early American law, the duty/tariff meaning predominates. For common law and equity researchers, be alert to the risk of encountering "customs" in the customary-law sense — particularly in property, land tenure, and local usage contexts.
Historical Dictionary Support
All five source dictionaries agree that customs, in the fiscal sense, refers to duties on imported and exported merchandise, and all trace the name to the same source: these payments were called customs because they had been paid from time immemorial, making them habitual obligations. This etymology is repeated without meaningful variation across Black's, Bouvier's, Anderson's, and Burrill's.
The most useful elaboration comes from Burrill, who cites Blackstone (1 Bl. Com. 313–315) and draws the express Latin distinction between custuma (fiscal customs) and consuetudines (usages/customs in the legal-practice sense). This distinction is the key to reading older sources correctly and is underemphasized in the other dictionaries.
Anderson's Dictionary provides the richest historical context, tracing the French and Latin roots and noting that customs were originally crown revenue claimed by prerogative — a framing that opens onto English constitutional history unavailable in the more skeletal entries in Black's.
Black's 2nd Ed. adds U.S. case citations absent from earlier editions, including the Pollock reference, signaling that by the early twentieth century customs had become embedded in federal constitutional litigation rather than merely in revenue administration. Researchers using the first edition of Black's for U.S. constitutional research should be aware of this gap.
None of the historical dictionaries address the modern agency meaning — U.S. Customs as an administrative bureaucracy — which emerged with the growth of the federal administrative state. That meaning must be researched through statutory and regulatory sources rather than these dictionaries.
Jurisdictional Note
In the United States, customs duties are exclusively federal — states may not levy their own duties on imports or exports under Article I, Section 10 of the Constitution. In other common law jurisdictions, the constitutional structure differs; researchers working with Canadian, Australian, or British materials should not assume the U.S. federal-exclusivity framework applies.
Encyclopedia Cross-Reference
The Law Mind Torts & Personal Injury Encyclopedia, torts_11: Negligence — Custom and Industry Practice as Evidence of Standard. This entry addresses the customary-law sense of customs as evidence of reasonable conduct in negligence litigation — a distinct but related concept for researchers working across tort and trade contexts.