Definition
In Latin legal usage, mare means the sea. The term appears in classical legal scholarship and early common law texts primarily in compound phrases that defined the legal status of the sea and navigable waters—whether open to all nations or subject to sovereign dominion.
The term carries no independent operative meaning in modern Anglo-American law. Its significance is almost entirely historical, arising from the great debate in seventeenth-century international law over whether the sea could be owned or controlled by a sovereign power.
Principal compound forms:
1. MARE CLAUSUM ("closed sea"): The sea as subject to sovereign ownership or exclusive dominion. Associated principally with John Selden's 1635 treatise Mare Clausum, written at the direction of the English Crown to counter Grotius and assert England's dominion over surrounding seas.
2. MARE LIBERUM ("free sea"): The sea as open to navigation and trade by all nations, incapable of private or sovereign ownership. The doctrine advanced by Hugo Grotius in his 1609 work of the same name, written to challenge Portuguese claims of exclusive maritime trade routes to the Indies.
3. MARE GRÆCORUM ("sea of the Greeks"): A term found in Bracton and other early legal sources referring to the Mediterranean Sea.
Common Language
Modern common usage (Wiktionary): An adult female horse; also, in informal usage, a foolish woman.
Historical common usage (Webster's 1913): The female of the horse and other equine quadrupeds.
The gap here is total. In legal Latin, mare has nothing to do with horses. The resemblance to the English word "mare" is coincidental — the Latin term derives from a distinct root meaning sea. Bouvier's handling of this is illustrative: his dictionary entry for MARE simply redirects the reader to HORSE, acknowledging the common English sense while confirming the term has no independent legal significance in that meaning. A researcher encountering "mare" in a Latin legal text should immediately read it as "sea," not as any equine reference.
Common Confusion
Mare (the sea) and mare (the female horse) are false cognates in a legal research context. The confusion is compounded in older English legal texts that mix Latin and English without translation. Additionally, researchers should not conflate mare clausum with territorial waters or the modern exclusive economic zone — these are related concepts in international law, but the historical doctrine of mare clausum is a broader and distinct claim of sovereign ownership over open sea, not merely a coastal buffer zone.
Why It Matters in Research
The term's primary research value is as a gateway to the mare clausum / mare liberum debate, which shaped centuries of international maritime law, admiralty doctrine, and the law of nations. Any researcher working in early modern admiralty, colonial trade law, or the history of international law will encounter these compound phrases repeatedly.
Trap for historical sources: Black's 1st edition gives only the bare Latin translation. The 2nd edition adds the essential compound forms and their significance. Burrill adds the Bracton reference to mare Græcorum. Bouvier deflects to HORSE entirely, which is unhelpful for legal research but does signal that the term had no operative English legal meaning on its own. Do not mistake Bouvier's redirect as indicating the term is unimportant — it reflects the dictionary's scope, not the doctrine's significance.
The mare clausum doctrine has direct connections to early English assertions of sovereignty over the British seas, the development of prize law, and the foundational tension between open navigation and coastal state authority that persists in modern UNCLOS frameworks. Researchers tracing the history of freedom of navigation should treat Selden and Grotius as primary sources, with Kent's Commentaries providing accessible synthesis for common law contexts.
Historical Dictionary Support
Black's 1st and 2nd editions agree on the core Latin translation. The 2nd edition is significantly more useful, adding the compound forms and citing Kent's Commentaries for doctrinal context. Burrill's entry is brief but adds textual grounding in Bracton, useful for researchers working with early common law sources. Bouvier's entry is the outlier — the redirect to HORSE suggests Bouvier treated the term as having English (equine) significance for his readers rather than Latin legal significance, or simply excluded the maritime doctrine as beyond his dictionary's common law scope.
None of the historical dictionaries adequately captures the full scope of the mare clausum debate or its downstream influence on admiralty and international law. For that, researchers must move beyond the dictionaries to the primary treatises and to Kent.
Jurisdictional Note
The mare clausum doctrine was never formally adopted as operative domestic law in the United States. Its significance in American research is historical and doctrinal — it informs the intellectual background of admiralty jurisdiction and freedom of navigation, but modern U.S. maritime law is governed by constitutional admiralty jurisdiction and international conventions, not the Selden framework.
Encyclopedia Cross-Reference
See Law Mind Encyclopedia — Mare Clausum; Freedom of the Seas; Admiralty and Maritime Law (Historical Foundations)