Definition
The high seas are the open waters of the ocean beyond the jurisdiction of any single nation — areas not subject to the territorial sovereignty of any state and open to use by all nations. The concept is the geographic and jurisdictional foundation of international maritime law.
Two overlapping meanings appear in legal sources:
1. Geographic meaning: The body of open ocean lying beyond coastal waters, harbors, bays, and other enclosed or semi-enclosed waters. Historically defined by reference to low-water mark on the seaward side and the fauces terrae (jaws of the land) on the landward side of coastal inlets.
2. Jurisdictional meaning: The area of ocean outside any nation's territorial sea, over which no state exercises sovereignty. Under modern international law as codified in the United Nations Convention on the Law of the Sea (UNCLOS, 1982), the high seas begin beyond the Exclusive Economic Zone — generally 200 nautical miles from a coastal baseline. Within the high seas, the principle of freedom of the seas applies: freedom of navigation, overflight, fishing, scientific research, and laying of submarine cables and pipelines.
The jurisdictional boundary is not fixed across history. It has shifted substantially from the common law era through the present, making the term's reach in any given source dependent entirely on when that source was written.
Common Language
Modern common usage (Wiktionary): "The regions of the ocean that are far from shore, especially those regions that do not belong to any country." Also used colloquially to describe unregulated regions of the internet where copyright infringement is prevalent.
Historical common usage (Webster's 1913): The open ocean, as distinguished from seas enclosed by headlands or within territorial limits of a nation.
The common meaning tracks the legal concept closely in broad strokes but misses the critical jurisdictional precision that makes the term operative in law. Colloquially, "high seas" suggests simply deep or distant ocean water. Legally, the boundary is a formal, contested, and historically shifting line that determines which nation's courts have criminal jurisdiction, which law governs maritime torts and contracts, and which remedies apply in admiralty proceedings. A researcher treating "high seas" as merely descriptive geography will misread jurisdictional holdings.
Common Confusion
High seas vs. territorial sea vs. contiguous zone vs. EEZ: These are not interchangeable. The territorial sea (historically 3 miles, now 12 nautical miles under UNCLOS) is subject to the coastal state's full sovereignty. The contiguous zone (up to 24 nautical miles) allows limited enforcement jurisdiction. The EEZ (up to 200 nautical miles) grants economic rights but not full sovereignty. The high seas begin only beyond the EEZ. Pre-UNCLOS sources often describe the high seas as beginning at the 3-mile limit, which directly contradicts modern international law. Reading nineteenth- and early twentieth-century cases with a modern jurisdictional map will produce errors.
Why It Matters in Research
The most important research trap with this term is temporal displacement of the boundary. Black's Law Dictionary reflects the traditional Anglo-American view that the high seas begin at low-water mark (excepting enclosed harbors and bays) — a definition that placed enormous swaths of coastal water within high-seas jurisdiction for purposes of criminal law and admiralty. American federal criminal statutes, including the Act of April 30, 1790, expressly extended federal jurisdiction over crimes committed "upon the high seas," and courts applied that phrase under the expansive early American definition. A researcher using a pre-UNCLOS case to answer a post-UNCLOS question — or vice versa — is working with incommensurable jurisdictional frameworks.
Second trap: the Death on the High Seas Act (DOHSA, 46 U.S.C. § 30301 et seq.) uses "high seas" as its operative geographic trigger, and the statute's application turns on whether an incident occurred within or beyond a fixed distance from shore. DOHSA's territorial limit has been litigated extensively, and the question of where the high seas begin for DOHSA purposes is distinct from where they begin under UNCLOS or under the general maritime law. Researchers should not assume that "high seas" means the same thing across these different legal instruments.
Third: criminal jurisdiction on the high seas under U.S. law runs through the Special Maritime and Territorial Jurisdiction statute (18 U.S.C. § 7), which incorporates its own definition of covered waters. The overlap between that definition, the admiralty jurisdiction of the federal courts, and the international law concept of high seas is imperfect and has generated persistent litigation.
For corpus researchers, the key navigational move is to identify the date and purpose of the source before extracting a boundary rule. The jurisdictional reach of any "high seas" holding is only as good as the era's agreed-upon definition of the term itself.
Historical Dictionary Support
Bouvier and Black agree on the core geographic formulation: the high seas are the unenclosed ocean waters beyond low-water mark, excluding harbors, bays, and inland waters enclosed by the fauces terrae. Bouvier cites Justice Story's circuit opinions (1 Gallison 624; 5 Mason 290) and Blackstone's Commentaries for the proposition that low-water mark, rather than any fixed offshore distance, marks the beginning of the high seas under American law — a deliberately expansive rule designed to ensure broad federal admiralty and criminal jurisdiction.
Black's adds the contrast between English and American doctrine explicitly: England historically adopted the three-mile limit as the seaward boundary of territorial waters (and therefore the starting point of the high seas), while American courts pushed the high seas inward to low-water mark. This divergence had real consequences for how courts on either side of the Atlantic analyzed crimes and torts occurring in coastal waters.
Neither Bouvier nor Black anticipated the modern international law structure of overlapping maritime zones. Their definitions describe a two-zone world — territorial waters and high seas — that UNCLOS replaced with a layered system of at least four distinct zones. The Rapalje & Lawrence entry retrieved is not responsive to this term (the text concerns English judicature reform) and contributes nothing to the analysis.
What the historical dictionaries miss entirely: the EEZ concept, freedom of the seas as a codified treaty right, flag-state jurisdiction as the default rule on the high seas, and the role of international tribunals in resolving high-seas disputes. Researchers relying solely on historical dictionary definitions will have no framework for any post-1945 maritime law question.
Jurisdictional Note
Under UNCLOS (to which the United States is not a party, though it treats most provisions as customary international law), the high seas begin at the outer edge of the EEZ, 200 nautical miles from baseline. U.S. domestic statutes may use narrower or broader definitions depending on the statute's own text and judicial interpretation. Courts applying DOHSA, the Jones Act, or federal criminal jurisdiction statutes each apply their own operative geographic boundaries, which may not align with each other or with international law.
Encyclopedia Cross-Reference
The Law of the Sea — UNCLOS, Territorial Waters, EEZ, and High Seas Jurisdiction (Law Mind Military, Veterans & Admiralty Law Encyclopedia): Primary reference for the modern international law framework, zone definitions, and freedom of the seas doctrine.
Death on the High Seas Act (DOHSA) — Pecuniary Damages, Territorial Limits, and Commercial Aviation (Law Mind Military, Veterans & Admiralty Law Encyclopedia): Essential for researchers working on maritime wrongful death claims and the jurisdictional trigger disputes under DOHSA.