Definition
The law of marque is a body of customary law governing the right of private reprisal — the authority of an aggrieved party to seize the ships or goods of a foreign nation's subjects when that party has suffered a legal wrong and cannot obtain ordinary justice through regular legal channels. Under this doctrine, a person or sovereign who has been wronged may, upon failure of normal legal redress, take the property of the wrongdoing party's compatriots wherever that property can be found within the aggrieved party's own territory or jurisdiction, treating the seizure as satisfaction for the original injury.
The law of marque is the underlying legal framework that gives meaning to letters of marque — the formal sovereign authorizations by which governments licensed private parties to carry out such reprisals. The "law" in this phrase refers to the customary and statutory rules governing when reprisal was permissible, what property could be taken, and under what procedural conditions the seizure was legitimate.
Common Confusion
The law of marque and letters of marque are related but distinct concepts. The law of marque is the legal doctrine — the rules defining when reprisal is justified and how it operates. Letters of marque are the instruments — official documents issued by a sovereign authorizing a specific individual to exercise reprisal under that doctrine. Confusion between the two is common in historical sources, which often use "marque" loosely to refer to either the authorization or the underlying legal right. Researchers should note that Bouvier and Burrill redirect to "Letter of Marque" without defining the law itself, which can obscure this distinction in historical research.
Why It Matters in Research
This term is largely obsolete in modern domestic law but remains significant in three research contexts.
First, constitutional research: The U.S. Constitution grants Congress the power to grant letters of marque and reprisal (Art. I, Sec. 8). Understanding the law of marque as the underlying doctrine clarifies what the Framers were authorizing — not mere privateering licenses in the modern military sense, but a recognized system of regulated private reprisal with roots in medieval commercial and international custom.
Second, historical international law: The law of marque sits at the intersection of customary international law, the law of nations, and early maritime law. Researchers working in 17th- and 18th-century sources will encounter this doctrine in discussions of sovereign relations, war, and commerce. The statutory reference in Rapalje & Lawrence to 27 Edw. III st. 2 c. 17 is a genuine anchor point — that statute formalized reprisal procedures in medieval England and is a traceable primary source.
Third, the doctrine illustrates the historical precursor to what became the law of neutrality and the legal framework for privateering. Understanding the law of marque helps researchers trace the evolution from private self-help reprisal to state-sanctioned commerce raiding to the abolition of privateering in the Declaration of Paris (1856).
A research trap: the term "marque" in historical sources sometimes refers only to the letter (the instrument) and sometimes to the broader legal right. Context is essential. Where a source says "law of marque," it typically means the doctrine; where it says simply "marque," it may mean the letter, the practice, or the right interchangeably.
Historical Dictionary Support
The historical dictionaries are thin and largely consistent on this term. Black's provides the most complete standalone definition, describing the law of marque as "a sort of law of reprisal" and capturing its essential mechanism: seizure of goods within one's own bounds when ordinary justice is unavailable. Rapalje & Lawrence tracks closely with Black's and usefully cites 27 Edw. III st. 2 c. 17, grounding the doctrine in English statutory history. Both sources cite Cowell and Brown — standard early-modern legal authorities — as their basis.
Bouvier and Burrill decline to define the term independently and redirect to "Letter of Marque," a choice that, while practical, causes the underlying doctrine to disappear from view. This is a meaningful gap: by collapsing the law into the instrument, these dictionaries obscure the fact that the right of reprisal existed conceptually prior to, and independently of, any letter. A researcher relying only on Bouvier or Burrill may miss the doctrinal framework entirely.
None of the four sources address the international law dimension of the doctrine, its relationship to the law of nations as theorized by Vattel or Grotius, or its abolition trajectory. For those dimensions, researchers must look beyond the dictionary shelf.
Jurisdictional Note
The law of marque as an operative doctrine has no application in modern U.S. or English domestic law. Its contemporary significance is constitutional (the letters of marque and reprisal clause) and historical. The Declaration of Paris (1856), to which the United States is not a formal signatory, effectively ended state-sanctioned privateering among major powers, rendering the practical law of marque a dead letter in international practice.
Encyclopedia Cross-Reference
See Law Mind Encyclopedia: Letters of Marque and Reprisal; Law of Nations; Privateering.