Territorial Sea

Also known as: territorial waters

Definition

The territorial sea is the belt of sea, up to 12 nautical miles wide, measured from a coastal state’s baselines, over which the state exercises sovereignty — the first and most complete of the maritime zones created by the United Nations Convention on the Law of the Sea (UNCLOS). Article 2 of Part II provides that this sovereignty “extends, beyond its land territory and internal waters and, in the case of an archipelagic State, its archipelagic waters,” to the territorial sea and to “the air space over the territorial sea as well as to its bed and subsoil.” Article 3 fixes the ceiling: “Every State has the right to establish the breadth of its territorial sea up to a limit not exceeding 12 nautical miles.” The sovereignty is real but qualified — ships of all states “enjoy the right of innocent passage through the territorial sea” under Article 17 — a regime distinct from the merely functional “sovereign rights” over resources that the exclusive economic zone grants, the distinction this wiki’s Exclusive Economic Zone entry documents. (UN — UNCLOS Part II, Wikipedia — Territorial waters)

The Philippines claims the zone through a statutory chain that begins with Republic Act No. 3046 (approved June 17, 1961), “An Act to Define the Baselines of the Territorial Sea of the Philippines,” whose straight baselines joining “appropriate points of the outermost islands of the archipelago” served as the measuring line for every later zone. The current law is the Philippine Maritime Zones Act, Republic Act No. 12064 (approved November 7, 2024), whose Section 5 defines the territorial sea as “the adjacent belt of sea measured twelve (12) nautical miles from the baselines,” with Philippine sovereignty over the sea, the airspace above it, and its seabed and subsoil, subject to UNCLOS — including innocent passage — and with the high-tide features of the Kalayaan Island Group each entitled to their own 12-nautical-mile territorial sea. (LawPhil — RA 3046, LawPhil — RA 12064)

Identities

Source	Identifier	URL
Wikipedia	Territorial waters	https://en.wikipedia.org/wiki/Territorial_waters
Wikidata	territorial sea (Q213204)	https://www.wikidata.org/wiki/Q213204
DBpedia	Territorial waters	https://dbpedia.org/page/Territorial_waters
ProductOntology	N/A	N/A
Wiktionary	territorial sea	https://en.wiktionary.org/wiki/territorial_sea
Library of Congress Subject Headings (LCSH)	N/A	N/A
MeSH	N/A	N/A
NCBI Taxonomy	N/A	N/A
AGROVOC	N/A	N/A
Google Scholar	territorial sea UNCLOS Article 2 innocent passage 12 nautical miles baselines Philippines	https://scholar.google.com/scholar?q=%22territorial+sea%22+UNCLOS+Philippines
ConceptNet	N/A	N/A
OpenCyc	N/A	N/A

Also Known As

territorial waters

Examples and Analogies

The sovereign porch of the national house: if internal waters are the house and archipelagic waters its fenced yard, the territorial sea is the porch — still the owner’s sovereign territory (water, seabed, subsoil, and air above), yet crossed by a protected easement: innocent passage for the ships of every state. (UN — UNCLOS Part II, Wikipedia — Territorial waters)
From cannon shot to twelve miles: the old three-mile limit was “originally… the distance of a cannon shot, hence the portion of an ocean that a sovereign state could defend from shore”; UNCLOS III replaced that measured-by-artillery logic with the uniform 12-nautical-mile belt that now governs all coasts. (Wikipedia — Territorial waters)
Sovereignty versus sovereign rights: the territorial sea and the EEZ are often confused. In the territorial sea the state owns the water itself; in the EEZ — this wiki’s separate entry — it holds only resource rights below the surface while the waters above stay open to all. Two zones, two grammars: dominion in the first, licensed exploitation in the second. (UN — UNCLOS Part II)
Rocks keep their porch but lose the yard: under Article 121, islands generate the full set of zones, but “rocks which cannot sustain human habitation or economic life of their own shall have no exclusive economic zone or continental shelf” — they keep at most a territorial sea, the rule that decides what disputed features are worth in maritime law. (UN — UNCLOS Part VIII)
Verified data (regime and Philippine instruments):
Treaty basis: UNCLOS Part II — Article 2 (sovereignty over sea, airspace, bed, subsoil), Article 3 (12-nautical-mile ceiling), Articles 17–19 (innocent passage and non-innocent acts), Article 33 (contiguous zone to 24 nautical miles) (UN — UNCLOS Part II)
First baselines statute: RA 3046, approved June 17, 1961 — straight baselines around the outermost islands; “all waters within the baselines… are considered inland or internal waters” (LawPhil — RA 3046)
Archipelagic baselines: RA 9522 (March 10, 2009) — 101 basepoints in WGS 84, Kalayaan Island Group and Bajo de Masinloc as a regime of islands under Article 121 (LawPhil — RA 9522)
Codification: RA 12064, approved November 7, 2024 — Section 5 territorial sea of 12 nautical miles; Section 2 names the West Philippine Sea to include “the territorial seas of Bajo de Masinloc and the maritime features of the Kalayaan Island Group”; Section 18 repeals portions of RA 3046 (LawPhil — RA 12064)
Islands regime: Article 121(3) — rocks generate no EEZ or continental shelf (UN — UNCLOS Part VIII)

Usage Scenarios

1. Measuring the Maritime Zones from the Baselines

Maritime lawyers and cartographers compute the zones in strict order — baselines first, then the 12-nautical-mile territorial sea, the 24-mile contiguous zone, and the 200-mile EEZ — so that every Philippine assertion, from fishery enforcement to the West Philippine Sea naming, starts from the same statutory lines. (UN — UNCLOS Part II, LawPhil — RA 12064)

2. Navigation and Law Enforcement at Sea

Navies, coast guards, and shipmasters apply the innocent-passage regime: passage must be “continuous and expeditious” under Article 18; Article 19 lists the activities that destroy innocence, from weapons exercises to intelligence collection; Article 20 requires submarines to navigate on the surface and show their flag; and Articles 24–25 balance the coastal state’s duty not to hamper passage against its right to protect itself. (UN — UNCLOS Part II)

3. Philippine Statutory Drafting and Maritime Governance

Congress and agencies now write the zones in one vocabulary: RA 12064 declares internal waters, archipelagic waters, the territorial sea, the contiguous zone, the EEZ, and the continental shelf in terms consistent with UNCLOS, repealing the surviving portions of the 1961 baselines act and citing the South China Sea Arbitration as a basis for exercising maritime rights. (LawPhil — RA 12064)

4. Classifying Disputed Features in the West Philippine Sea

Where the West Philippine Sea disputes engage the zone, the operative question is often what a feature generates: the 2016 Annex VII tribunal classified Scarborough Shoal, Cuarteron Reef, Fiery Cross Reef, Johnson Reef, McKennan Reef, and Gaven Reef (North) as high-tide features, and Hughes Reef, Gaven Reef (South), Subi Reef, Mischief Reef, and Second Thomas Shoal as low-tide elevations — the former entitled at most, as rocks, to a territorial sea under Article 121. (Wikipedia — South China Sea Arbitration, UN — UNCLOS Part VIII)

Strategies

Keep sovereignty and sovereign rights grammatically separate. Write “sovereignty” only for the territorial sea, archipelagic waters, and internal waters; write “sovereign rights” for EEZ resources — the standard formulation that keeps the West Philippine Sea arguments legally legible. (UN — UNCLOS Part II)
Anchor every zone to the baselines statute in force. The Philippine territorial sea is measured from the baselines of RA 3046 as redrawn by RA 9522 and restated by RA 12064 — the chain this wiki’s Exclusive Economic Zone entry documents in detail. (LawPhil — RA 9522, LawPhil — RA 12064)
Use the median line for overlapping belts. Where neighboring coasts lie within 24 nautical miles of each other, UNCLOS Article 15 points to the median line absent agreement or special circumstances — the delimitation default for opposite and adjacent states. (UN — UNCLOS Part II)
State the archipelagic position precisely. The Philippines is an archipelagic state whose waters inside the baselines are archipelagic waters — not internal waters as the 1961 act claimed, and not territorial sea — with passage regimes RA 12064 now restates. (LawPhil — RA 3046, LawPhil — RA 12064)

Security and Safety Measures

Comply with innocent passage, not merely claim it. Transiting vessels must keep to continuous and expeditious passage, avoid the Article 19 activities that destroy innocence, and — for submarines — surface and show the flag. (UN — UNCLOS Part II)
Distinguish the zones when enforcing. Boarding, arrest, and detention powers differ by zone: full territorial law in the territorial sea, resource-oriented enforcement in the EEZ under Article 73; misapplying one regime to the other is itself a violation. (UN — UNCLOS Part II, Wikipedia — Territorial waters)
Preserve the paper trail at sea. Incidents inside contested territorial seas should be documented — position, time, conduct — since the 2016 award shows how decisive the record of conduct at specific features can be. (Wikipedia — South China Sea Arbitration)
Publish charts and deposit them. Article 16 requires coastal states to give due publicity to baselines and outer limits and deposit charts with the UN Secretary-General — the transparency duty that lets other states know exactly where the 12-mile belt lies. (UN — UNCLOS Part II)

Historical Context

The belt was not always twelve miles wide. The three-mile cannon-shot limit held from the eighteenth century among Britain, the United States, and France until the mid-twentieth century; the Truman proclamations of September 28, 1945 broke the old ceiling by claiming continental-shelf resources; and only UNCLOS III (1973–1982) settled the modern 12-nautical-mile breadth, which entered into force with the Convention in 1994. (Wikipedia — Territorial waters)

The Philippines legislated before the treaty caught up. RA 3046 of 1961 drew straight baselines around the archipelago’s outermost islands and declared the waters inside them internal waters, in a preamble that framed the nation’s maritime claims through the Treaty of Paris of December 10, 1898 and its successor treaties — the treaty-limits posture that defined Philippine baselines law for almost half a century and that RA 5446 amended in 1968. When the country ratified UNCLOS in 1984 as an early party, its baselines had to be reconciled with the Convention’s archipelagic-state rules; RA 9522 of March 10, 2009 performed the conforming amendment, replacing the old straight lines with archipelagic baselines through 101 basepoints. (LawPhil — RA 3046, LawPhil — RA 9522)

The 2016 award shaped the zone’s Philippine application. In the arbitration the Philippines instituted in 2013, the tribunal held the Spratlys’ high-tide features to be rocks under Article 121(3), entitled to no EEZ or continental shelf, and expressly declined to rule on sovereignty over any feature or to delimit any boundary — leaving the territorial seas of the disputed features, inside the nine-dash-line overlap this wiki’s Nine-Dash Line and Philippines v. China entries document, as the zone where entitlement is conceded even while ownership is contested. RA 12064 of November 7, 2024 then restated the entire architecture in national law. (Wikipedia — South China Sea Arbitration, LawPhil — RA 12064)

Challenges and Controversies

Sovereignty Contested, Entitlement Conceded

The territorial seas around the West Philippine Sea features are the dispute’s irreducible core: the 2016 tribunal ruled on what the features generate under UNCLOS while stating it “would not rule on any question of sovereignty… and would not delimit any” boundary — so both the Philippine and Chinese positions continue to assert sovereignty over features whose 12-mile belts overlap. (Wikipedia — South China Sea Arbitration)

The Treaty-Limits Posture and the Archipelagic Doctrine

RA 3046’s claim that all waters inside its baselines were internal waters — resting on the Treaty of Paris rectangle recited in its preamble — sat uneasily with UNCLOS’s archipelagic-waters regime, under which waters inside archipelagic baselines are a distinct category subject to sea-lanes passage. The 2009 and 2024 statutes settled Philippine practice on the UNCLOS vocabulary, but the older posture persists in public argument about the extent of the national maritime domain. (LawPhil — RA 3046, LawPhil — RA 12064)

Innocent Passage and Foreign Warships

The innocent-passage regime is the belt’s standing friction point: Article 19’s list of non-innocent activities and Article 20’s submarine-surfacing rule govern foreign naval transit, while Article 24 forbids the coastal state to hamper passage — a balance each incident at sea re-tests. (UN — UNCLOS Part II)

The Naming Overlay

Section 2 of RA 12064 defines the West Philippine Sea to include “the territorial seas of Bajo de Masinloc and the maritime features of the Kalayaan Island Group,” folding the disputed belts into the statutory name — nomenclature that frames but cannot itself resolve the underlying contest this wiki’s West Philippine Sea entry records. (LawPhil — RA 12064)