Comprehensive Notes on the International Law of the Sea
Core Tensions and Historical Development of the Law of the Sea
Ocean Resources and Strategic Significance:
Oceans cover more than of the Earth's surface.
Over of global trade is transported by sea, according to International Maritime Organization (IMO) estimates.
Projecting naval power across ocean expanses serves as a foundational pillar of military doctrine for the United States and other maritime powers.
Offshore drilling accounts for of global oil production.
Living and non-living ocean resources encompass:
Coastal fisheries: Located close to shorelines, traditionally exploited by nationals of the coastal state.
Long-distance fisheries: Utilized by distant-water fishing nations across the globe.
Mineral deposits: Manganese nodules and polymetallic sulfides situated on the deep ocean floor.
Cultural resources: Historical shipwrecks resting on the seabed.
Environmental regulation: Marine debris mitigation, pollution control, and climate and weather pattern regulation.
Historical Evolution of Ocean Governance (–):
The central legal tension in ocean governance has historically existed between maritime powers asserting freedom of navigation and coastal states asserting sovereign control over offshore resources.
Between and , Spain and Portugal sought to enclose vast expanses of the ocean and exclude rival emerging maritime powers, namely England and The Netherlands.
In , following an Amsterdam prize case concerning the capture of a richly laden Portuguese merchant vessel by the Dutch East India Company, the Dutch lawyer Hugo de Groot (Grotius) was commissioned to draft a legal justification.
In , a chapter of Grotius's tract was published anonymously as Mare Liberum (Freedom of the Seas).
Grotius established the legal principle that oceans are international territory open to all nations, limiting coastal state jurisdiction to a narrow band offshore.
By , Grotius's doctrine had prevailed, enduring until the end of World War II.
The historical seaward limit of coastal state sovereignty was defined by the "cannon shot rule" (the physical limit of shore-based projectile force), fixed at one marine league or (a nautical mile being slightly longer than a land statute mile).
Post-World War II Shift and the United Nations Conferences:
Following , the balance of ocean rights shifted heavily toward coastal states. The United States, despite being the world's preeminent naval power, sought extensive regulatory control over its adjacent offshore natural resources.
First UN Conference on the Law of the Sea (UNCLOS I, , Geneva) produced four conventions and an optional protocol on compulsory dispute settlement:
Convention on the Territorial Sea and the Contiguous Zone.
Convention on the High Seas.
Convention on the Continental Shelf.
Convention on Fishing and Conservation of the Living Resources of the High Seas.
Second UN Conference on the Law of the Sea (UNCLOS II, ):
Failed to achieve consensus regarding the precise breadth of the territorial sea.
Post- Claims:
During the and , developing states across Latin America, the Caribbean, and Africa declared territorial seas and resource jurisdictions extending to or beyond, prompting diplomatic conflict with naval powers.
Third UN Conference on the Law of the Sea (UNCLOS III, –):
The longest diplomatic negotiation in international legal history, convened to draft an overarching "constitution for the oceans."
Culminated in the United Nations Convention on the Law of the Sea (UNCLOS or LOST).
The United States and UNCLOS Ratification:
The United States objected to the Part XI deep seabed mining regime and declined to sign the treaty text.
In , an Agreement Relating to the Implementation of Part XI was concluded, amending deep seabed mining provisions toward market-oriented structures; the United States signed this agreement.
Ratification requires a majority vote in the United States Senate, which has consistently withheld advice and consent.
Substantive United States policy treats the vast majority of UNCLOS provisions as codifications of binding customary international law.
Proponents across Republican and Democratic administrations, alongside diverse industrial and environmental interest groups, advocate ratification to secure treaty-based stability, legal clarity, and institutional leverage.
Baselines and Internal Waters
The Role and Delimitation of Baselines:
Maritime zones are measured seaward from designated baselines.
On an uncomplicated coast, the legal baseline follows the low-water mark along the coast as marked on large-scale charts officially recognized by the coastal state.
Coastal complexities altering baseline geometry include:
Deep coastal indentations and bays.
Barrier islands and fringing island chains.
Human-made installations, including permanent harbor works and offshore lighthouses anchored on exposed rocks.
Rising sea levels cause baseline points to shift landward (ambulatory baselines), creating disadvantages for low-lying coastal and island states.
Legislative measures enacted by coastal states to unilaterally freeze baselines against environmental changes lack universal recognition by third-party states under existing treaty rules.
Legal Status of Internal Waters (IW):
Internal waters comprise all water bodies located on the landward side of the baseline, including rivers, lakes, canal systems, ports, and enclosed bays.
Internal waters are assimilated into the terrestrial sovereignty of the coastal state; the state exercises absolute territorial sovereignty over events occurring within them.
Exceptions to Coastal State Sovereignty in Internal Waters:
Treaty Servitudes: International conventions that grant access or transit rights to foreign states across another state's internal waterways (e.g., the Treaty of Versailles designating the Kiel Canal across northern Germany as an international waterway open to all nations at peace).
Port Access for Commercial Vessels:
Customary law recognizes an absolute right of port entry only for foreign vessels experiencing maritime distress (force majeure).
Coastal states maintain authority to condition foreign vessel port access, provided such rules are non-discriminatory, reasonable, and promulgated in good faith (such as environmental compliance and anti-pollution mandates).
Jurisdictional Allocation: Internal management and onboard civil discipline have historically been reserved to the vessel's flag state; however, modern state practice permits the coastal port state to exercise jurisdiction over foreign commercial ships regarding environmental violations, local safety threats, and dockside labor conditions.
Territorial Seas and International Straits
Breadth and Sovereign Scope of the Territorial Sea (TS):
UNCLOS expanded the breadth of the territorial sea from the historic to a maximum width of , measured from coastal baselines.
Sovereignty of the coastal state extends to the water column, the seabed, the subsoil, and the superjacent national airspace above the territorial sea.
The Regime of Innocent Passage:
Defined as navigation through the territorial sea for the purpose of traversing that sea without entering internal waters, or proceeding to or from internal waters.
Passage must be continuous and expeditious.
Passage is innocent so long as it is not prejudicial to the peace, good order, or security of the coastal state.
Coastal states cannot levy fees for passage or apply discriminatory measures, though they may temporarily suspend innocent passage in specified areas of their territorial sea for essential national security reasons.
Coastal state civil and criminal jurisdiction over passing foreign vessels is restricted to instances where the consequences of a crime extend to the coastal state, disturb local tranquility, involve illicit narcotics trafficking, or are requested by the ship's master or flag state.
Non-Innocent Passage Criteria and Warships:
UNCLOS Article 19 enumerates activities rendering passage non-innocent, such as:
Any threat or use of force against the sovereignty of the coastal state.
Exercises or practices involving weapons of any kind.
Intelligence gathering or acts of propaganda aimed at coastal defenses.
Launching, landing, or taking onboard military devices or aircraft.
Willful and serious pollution.
Unauthorized fishing or research operations.
Direct interference with communications networks or coastal facilities.
Coastal states have claimed authority to require prior notification or authorization for foreign warships entering territorial waters; naval powers (including the United States, the United Kingdom, and Russia) reject this constraint as inconsistent with customary navigation rights.
The Doctrine of Transit Passage in International Straits:
Established during UNCLOS III negotiations as the naval powers' explicit condition (quid pro quo) for accepting the global expansion of territorial seas to .
Applies to straits used for international navigation connecting one part of the high seas or an exclusive economic zone to another part of the high seas or an exclusive economic zone (e.g., the Strait of Gibraltar, the English Channel, the Strait of Hormuz at the entrance to the Persian Gulf).
The International Court of Justice determined that the phrase "used for international navigation" must be construed broadly based on geographical layout and actual transit use.
Coastal states bordering straits have minimal authority to interfere with civilian or military traffic.
Submarines are permitted to transit submerged, surface warships need not obtain prior authorization, and military aircraft retain overflight rights.
Coastal states are legally prohibited from suspending transit passage under any circumstances, even during periods of international crisis.
The Contiguous Zone
Spatial Limits and Functional Jurisdiction:
The contiguous zone (CZ) extends from the seaward boundary of the territorial sea at out to an outer limit of from the baseline.
The contiguous zone is not an area of coastal state sovereignty; rather, it confers specific regulatory enforcement authority.
Coastal states may exercise control necessary to:
Prevent infringement of its customs, fiscal, immigration, or sanitary (CFIS) laws and regulations within its territory or territorial sea.
Punish infringement of those above-mentioned laws committed within its territory or territorial sea.
Historical Context and Legal Nature:
Established to counter the rigid legalism of baseline-adjacent boundaries utilized by smugglers.
Early nineteenth-century high-tariff regimes created large-scale coastal smuggling; foreign "mother ships" hovered immediately beyond the historic boundary while smaller craft moved contraband ashore, avoiding law enforcement.
Rum-runners employed identical tactics during United States Prohibition, mirroring methods utilized by modern offshore narcotics traffickers.
Chief Justice John Marshall of the United States Supreme Court described contiguous enforcement as an ongoing "struggle for law": foreign states submit to enforcement if actions are reasonable and necessary to secure domestic laws against violation, but will resist if such controls unnecessarily vex and harass lawful foreign maritime commerce.
Enforcement Boundaries and Underwater Cultural Heritage:
General security regulations were proposed for coastal inclusion in the contiguous zone during treaty drafts, but were rejected during UNCLOS negotiations.
Coastal states may control traffic in and removal of underwater cultural property and historic shipwrecks within , consistent with the UNESCO Convention on the Protection of the Underwater Cultural Heritage.
The Continental Shelf and the Exclusive Economic Zone
The Continental Shelf (CS) Regime:
Legal Evolution through "Instant Custom":
In , United States President Harry S. Truman issued Presidential Proclamation No. (the Truman Proclamation).
The proclamation declared the natural resources of the subsoil and seabed of the continental shelf contiguous to the United States coast as "appertaining to the United States, subject to its jurisdiction and control."
Prompted by domestic petroleum supply concerns after World War II and the discovery of reachable offshore oil reserves in the Gulf of Mexico.
Widespread adoption of similar claims created customary international law by the time of the UNCLOS I.
Codification and Limits:
The Convention on the Continental Shelf set the outer limit at a water depth of or, beyond that, to where the depth of superjacent waters admitted the exploitation of natural resources (the "exploitability test").
The UNCLOS established a baseline minimum legal continental shelf extending out to regardless of actual geological seabed characteristics.
Extended Continental Shelf: Where the physical continental margin extends beyond , coastal states may submit technical data to the UN Commission on the Outer Limits of the Continental Shelf (CLCS) to establish an extended continental shelf, capped at a maximum of from the baseline (or beyond the isobath).
Article 82 Revenue Sharing:
Coastal states exploiting non-living resources on the continental shelf beyond must make annual financial payments or contributions in kind via the International Seabed Authority (ISA) in Kingston, Jamaica.
The ISA is mandated to distribute these proceeds to states parties based on equitable sharing criteria, taking into account the interests of developing states, particularly landlocked and least developed nations.
Administrative and institutional challenges include defining accounting formulas, determining enforcement mechanisms for default, and addressing the lack of direct participation from least developed states compared to commercial extractive contractors.
The Exclusive Economic Zone (EEZ) Regime:
Established under UNCLOS to accommodate the conflicting claims of developing states and major maritime powers; entered into force after developing states claimed extensive resource zones between and .
The United States proclaimed its own EEZ in .
Geographical limit: Extends from the outer boundary of the territorial sea () up to a maximum distance of from coastal baselines.
Coastal State Rights:
Sovereign rights for exploring, exploiting, conserving, and managing natural resources of the water column, seabed, and subsoil (predominantly fisheries, tidal energy, and hydrocarbons).
Jurisdiction over the establishment and use of artificial islands and offshore installations, marine scientific research, and protection of the marine environment.
Preserved Freedoms for Non-Coastal States:
Non-coastal states retain high seas freedoms of navigation, overflight, and the laying of submarine cables and pipelines within the EEZ.
Fisheries Enforcement and Management:
Overfishing of apex commercial species (tuna, salmon, sea bass) drives persistent enforcement actions.
In , Canada and Spain engaged in the "Turbot War" in the North Atlantic; Canadian enforcement vessels fired warning shots at and seized the Spanish fishing vessel Estai operating just outside Canada's EEZ boundary.
UNCLOS Article 73 stipulates that arrested foreign fishing vessels and crews must be promptly released upon the posting of a reasonable bond or financial security.
The UN Straddling Fish Stocks Agreement closed legal gaps governing fish populations moving across EEZ boundaries into adjacent high seas zones.
The High Seas and Deep Seabed Exploitation
Juridical Status of the High Seas (HS):
Encompasses all maritime areas not included within the internal waters, territorial sea, archipelagic waters, or exclusive economic zone of any state.
Governed by the open seas principle: reserved for peaceful purposes, with no state entitled to subject any portion of the high seas to its national sovereignty.
High seas freedoms include navigation, overflight, submarine cable/pipeline deployment, artificial island construction, scientific research, and fishing.
Flag State Jurisdiction and High Seas Order:
Ships must sail under the flag of a single state with a genuine link between vessel and state.
Flag states oversee Construction, Design, Equipment, and Manning (CDEM) standards, harmonized by the International Maritime Organization (IMO) based in London.
Right of Visit: Warships on the high seas may board foreign vessels when reasonable grounds exist to suspect:
Piracy.
Slave trading.
Unauthorized broadcasting from the high seas.
Statelessness (flying no flag or refusing to show a flag).
Flying a fraudulent flag or concealing actual nationality.
Modern piracy hotspots requiring security actions include the Gulf of Guinea, the Caribbean, the South China Sea, and waters off Somalia in the Horn of Africa.
Maritime Interdiction: Subject to international human rights laws, refugee conventions, and multilateral frameworks regarding weapons of mass destruction (WMD) interdictions and anti-narcotics enforcement.
Historical Belligerent Rights and Communication Infrastructure:
Prize Law: The capture of enemy and neutral vessels during armed conflict sparked historic conflicts (e.g., British seizures of American ships serving as the casus belli for the War of , and the Trent Affair nearly bringing Britain into the American Civil War).
Blockades and Exclusion Zones: Imposed under sovereign operational declarations, such as the United States naval "quarantine" during the – Cuban Missile Crisis, German submarine exclusion zones in World Wars I and II, and British/Argentine exclusion zones during the Falklands/Malvinas War.
Submarine Fiber-Optic Cables:
Over of deep-sea fiber optic cables handle over of all international telecommunications and digital data.
International legal frameworks contain regulatory protection gaps regarding intentional disruptions or sabotage to underwater communication backbones.
The Deep Seabed ("The Area") and the International Seabed Authority (ISA):
Extends to the seabed, ocean floor, and subsoil beyond the limits of national jurisdiction.
Spurred by Arvid Pardo's United Nations General Assembly address, the Area and its mineral deposits (manganese nodules containing nickel, copper, cobalt, and polymetallic sulfides) were declared the "common heritage of mankind."
Governed by the International Seabed Authority (ISA) based in Kingston, Jamaica, with plus the European Union.
Regulatory Structure:
Includes "The Enterprise," a theoretical direct-mining commercial arm of the ISA.
Over have been issued to state enterprises and private contractors.
The ISA operates under a dual mandate: conserve deep ocean habitats from serious injury while establishing an exploitation code to extract seabed minerals.
Biodiversity and Unilateral Exploitation Developments:
The Agreement on the Conservation and Sustainable Use of Marine Biological Diversity of Areas Beyond National Jurisdiction (BBNJ Treaty) was concluded under UNCLOS, requiring to enter into force.
In April , the United States issued an executive order directing the National Oceanic and Atmospheric Administration (NOAA) to accelerate commercial recovery permits for deep-seabed minerals outside United States territorial waters.
The ISA asserts that deep seabed resources within the Area cannot be exploited unilaterally outside the legal framework of UNCLOS, regardless of a nation's non-party status.
Maritime Delimitation and Boundary Disputes
Principles Governing Overlapping Claims:
Where opposite or adjacent coastal states are separated by less than , their claims to territorial seas, EEZs, or continental shelves overlap, requiring maritime delimitation.
States are legally obligated to pursue good-faith bilateral negotiations to achieve an equitable delimitation agreement.
UNCLOS Articles 74 (EEZ) and 83 (Continental Shelf) mandate that delimitation lines achieve an "equitable solution."
Methodological Delimitation Frameworks:
The Equidistance/Median Line Principle:
Draws a line where every point is equidistant from the nearest points of the baselines of the respective coastal states.
In the North Sea Continental Shelf Cases (), the International Court of Justice (ICJ) rejected the mandatory use of the equidistance method under customary law because Germany's concave coastline caused an inward "cutoff effect," rendering it artificially "zone-locked" between Denmark and the Netherlands.
Special Circumstances and Equitable Adjustments:
International tribunals employ a three-stage delimitation procedure: construct a provisional equidistance line, identify relevant/special circumstances that justify adjusting the line to prevent distortive effects, and conduct a disproportionality test.
Special circumstances include coastal concavity, historical user rights, presence of atypical offshore islands, and coastline configurations.
Proportionality tests compare the ratio of maritime area assigned to each state with the ratio of their coastal frontage lengths.
Tribunals consistently reject macroeconomic disparities, relative national wealth, or land-based geological differences between states as legally relevant criteria.
Adjudicated Case Studies and State Practice:
Bay of Bengal Delimitations:
Decades of stalemated negotiations between Bangladesh, Myanmar, and India were resolved via compulsory international dispute procedures.
International Tribunal for the Law of the Sea (ITLOS) ( Bangladesh v. Myanmar) and an Annex VII Arbitral Tribunal ( Bangladesh v. India) adjusted provisional equidistance lines to account for Bangladesh's concave coastline and mitigate the coastal cutoff effect.
Tribunals delimited overlapping extended continental shelves beyond , creating jurisdictional "gray areas" where one state retains sovereign rights over the seabed subsoil while another state exercises jurisdiction over the superjacent water column.
Treatment of Offshore Islands and Reef Features:
Under UNCLOS Article 121, naturally formed islands capable of sustaining human habitation or economic life generate a full suite of maritime zones ( TS, CZ, EEZ, and a continental shelf).
Rocks that cannot sustain human habitation or economic life are denied an EEZ or continental shelf, generating only a territorial sea.
Small formations, such as the Isle of Palmas or Hans Island, alter vast maritime allocations if classified as islands.
In delimited straits or narrow seas, international practice often gives partial or zero effect to foreign-owned islands positioned close to a foreign mainland coast (e.g., the Greek islands adjacent to Turkey, or the British Channel Islands situated off the French coast).
South China Sea Delimitation and the Philippines v. China Arbitration:
China has built over of artificial features across seven coral reefs in the Spratly Island chain since , installing military installations to reinforce historic maritime claims.
In , the Philippines initiated compulsory arbitration under UNCLOS Annex VII against China, challenging the legal validity of China's "nine-dash line," which encompasses approximately of the Philippine EEZ.
The Philippines filed an initial memorial approaching containing over , followed by a supplemental submission to the five-member arbitral panel.
China boycotted direct proceedings, publishing an official diplomatic white paper asserting that the tribunal lacked subject-matter jurisdiction because the claims concerned territorial sovereignty and military affairs, which China excluded under its UNCLOS declarations.
Vietnam filed a formal statement of opposition against China's nine-dash line with the tribunal, supporting the Philippines' legal challenge.
In its arbitral award, the tribunal ruled that China's historic rights claims within the nine-dash line were incompatible with UNCLOS, and that none of the Spratly features were legally capable of generating an EEZ or continental shelf; China declared the ruling null and void, refusing compliance.
Questions & Discussion
Question: Why shouldn't tribunals consider economic disparities between states in delineating maritime boundaries, or should they? Would this be one way to create a more level playing field among states?
International jurisprudence treats maritime delimitation as an objective spatial exercise designed to apportion zones based strictly on coastal geography (the principle that "the land dominates the sea").
Wealth and economic power fluctuate over time, whereas maritime boundaries are designed to provide permanent legal certainty and stability; factoring economic disparities into boundary lines could invite boundary revisions whenever a state's economic conditions change.
Conversely, some legal scholars argue that equitable principles under UNCLOS Articles 74 and 83 should consider socioeconomic needs, such as coastal communities' reliance on artisanal fisheries, to avoid worsening resource disparities between wealthy and developing states.
Question: What incentives might lead states to negotiate an international treaty to preserve a natural resource?
Addressing the "tragedy of the commons" in shared maritime spaces, where unregulated, competitive exploitation leads to the collapse of high-seas fisheries, mineral reserves, or shared water columns.
Ensuring resource stability, economic predictability, and conflict de-escalation by agreeing on fixed conservation quotas and licensing systems.
Gaining multilateral legitimacy, institutional standing, and access to shared scientific research or revenue-sharing arrangements (such as benefits distributed by the International Seabed Authority).
Substantive state practice, international jurisprudence, and the official policy of major maritime nations (such as the United States) treat the vast majority of provisions within the 19821982 United Nations Convention on the Law of the Sea (UNCLOS) as codifications of binding customary international law, while excluding its conventional Part XI deep seabed mining regime.
Baselines and Internal Waters
Delimitation of Baselines:
The low-water line along the coast, as marked on officially recognized large-scale charts, serves as the standard baseline.
Straight baselines across deeply indented coasts, fringing islands, or river mouths are recognized under customary law.
Sovereignty over Internal Waters:
Waters located landward of the baseline are assimilated into the terrestrial sovereignty of the coastal state, granting complete territorial jurisdiction over events occurring within them.
Port Entry Rights:
Customary international law recognizes an absolute right of foreign vessel entry only in circumstances of maritime distress (force majeure).
Coastal states maintain customary authority to condition port entry on reasonable, non-discriminatory safety and environmental criteria.
Territorial Seas and Straits
Breadth of the Territorial Sea:
Coastal state sovereignty extends up to a maximum limit of 12 nautical miles12nautical miles from coastal baselines, encompassing the water column, seabed, subsoil, and superjacent national airspace.
Regime of Innocent Passage:
Foreign commercial vessels and warships possess the customary right of continuous and expeditious passage through the territorial sea, provided transit is not prejudicial to the peace, good order, or security of the coastal state.
Coastal states cannot levy transit fees, discriminate against flag states, or routinely assert civil or criminal jurisdiction over foreign ships in transit.
Major naval powers treat warship transit without prior notification or authorization as a customary navigational entitlement.
Transit Passage in International Straits:
Applies to straits used for international navigation linking one area of high seas or exclusive economic zone to another (construed broadly based on geographical layout and actual use, as affirmed by the International Court of Justice).
Guarantees unimpeded, non-suspendable navigation and overflight for civilian and military vessels in their normal operational mode, including submerged transit for submarines and aerial overflight without prior clearance.
Contiguous Zone
Functional Enforcement Jurisdiction:
Coastal states may exercise regulatory control in an area extending from 12 nautical miles12nautical miles to 24 nautical miles24nautical miles from coastal baselines.
Authority is limited to preventing and punishing infringements of customs, fiscal, immigration, or sanitary (CFIS) laws committed within the coastal state's land territory or territorial sea.
Underwater Cultural Heritage:
Coastal states exercise regulatory jurisdiction over historical shipwrecks and underwater cultural artifacts within 24 nautical miles24nautical miles.
Continental Shelf
Sovereign Rights over Seabed Resources:
Coastal states exercise sovereign rights for exploring and exploiting the non-living resources (hydrocarbons, minerals) and sedentary living species of the seabed and subsoil.
Recognized as "instant custom" following the 19451945 Truman Proclamation.
Extends to a minimum of 200 nautical miles200nautical miles from baselines, regardless of geological characteristics, and up to 350 nautical miles350nautical miles (or 100 nautical miles100nautical miles beyond the 2,500 meter2,500meter isobath) where physical continental margins extend beyond 200 nautical miles200nautical miles.
Exclusive Economic Zone (EEZ)
Resource Jurisdiction out to 200 nautical miles200nautical miles:
Coastal states possess sovereign rights over exploring, exploiting, conserving, and managing natural living resources (fisheries) and non-living resources within the water column, seabed, and subsoil.
Jurisdiction over marine scientific research, environmental protection, and artificial installations.
Preserved High Seas Freedoms:
Non-coastal states retain high seas freedoms of navigation, overflight, and the laying of submarine cables and pipelines within foreign EEZs.
Fisheries Enforcement:
Customary requirement (codified in Article 7373) that arrested foreign fishing vessels and crews must be promptly released upon posting a reasonable bond or financial security.
High Seas Freedoms and Order
The Principle of Mare Liberum:
High seas are open to all nations and reserved for peaceful purposes; no state may validly subject any portion of the high seas to national sovereignty.
Universal freedoms include navigation, overflight, fishing, scientific research, and deploying submarine cables/pipelines.
Flag State Exclusivity:
Ships must sail under the flag of a single nation with a genuine link, with the flag state maintaining exclusive regulatory oversight over Construction, Design, Equipment, and Manning (CDEM) standards.
Warship Right of Visit:
Warships may lawfully board foreign vessels on the high seas when reasonable grounds exist to suspect piracy, slave trading, unauthorized high-seas broadcasting, statelessness, or fraudulent concealment of nationality.
Non-Customary Exception: Deep Seabed Mining (Part XI)
Conventional Nature of Part XI:
The institutional, regulatory, and production-sharing rules governing "The Area" and the International Seabed Authority (ISA) are conventional treaty rules binding only on state parties to UNCLOS, rather than general customary international law.