State territorial sovereignty: acquisition, restrictions and loss

1. Meaning

Territorial sovereignty is the right of a State to exercise, within a portion of the globe and to the exclusion of any other State, the functions of a State. That is Max Huber's definition in the Island of Palmas award (1928). Territory includes land, internal waters, the territorial sea, the airspace above them and the subsoil beneath.

2. Modes of acquisition

(1) Occupation. Acquisition of terra nullius, territory belonging to no State. Requirements: the territory must be terra nullius; there must be an intention to act as sovereign (animus); and there must be effective occupation, a continuous and peaceful display of State authority (corpus). Territory inhabited by tribes having social and political organisation is not terra nullius (Western Sahara, ICJ advisory opinion, 1975). Discovery alone gives only an inchoate title, which must be completed by effective occupation within a reasonable time.

• Island of Palmas (Netherlands v. USA, Permanent Court of Arbitration, 1928, Max Huber). The US claimed the island as successor to Spain, which had discovered it in the sixteenth century; the Netherlands relied on peaceful and continuous display of authority through the Dutch East India Company and local rulers since about 1700. Held for the Netherlands. Discovery gave Spain only an inchoate title, which had not been perfected; a title must also be maintained according to the law of each period (intertemporal law).
• Clipperton Island (France v. Mexico, arbitration by the King of Italy, 1931). France proclaimed sovereignty in 1858 over an uninhabited island and did little more. Held for France: for an uninhabited and inaccessible place, very little actual exercise of authority is needed.
• Legal Status of Eastern Greenland (Denmark v. Norway, PCIJ, 1933). Norway occupied part of East Greenland in 1931. Held for Denmark: in thinly populated areas, little actual exercise of sovereign rights suffices if the other State cannot show a superior claim. The Norwegian Foreign Minister's oral assurance (the Ihlen declaration, 1919) that Norway would not make difficulties was also binding.

(2) Prescription. Acquisition of territory belonging to another State through continuous and undisturbed exercise of sovereignty over a long period, so that the original owner is taken to have acquiesced. There is no fixed period. Protest by the original owner prevents prescription. Example: the Chamizal arbitration (USA v. Mexico, 1911) rejected a US claim by prescription because Mexico had protested. Minquiers and Ecrehos (France v. UK, ICJ, 1953) awarded the islets to the UK on the strength of the actual exercise of authority (local administration, taxation, jurisdiction) rather than ancient feudal titles.

(3) Accretion. Increase of territory by natural causes, such as deposits forming new land at a river mouth or a new island rising in the territorial sea. No formal act is needed. Avulsion (a sudden change of a river's course) does not shift the boundary.

(4) Cession. Transfer of territory by one State to another by treaty, by sale, gift or exchange: the sale of Alaska by Russia to the US (1867); the exchange of Heligoland and Zanzibar between Britain and Germany (1890); the transfer of Pondicherry by France to India (treaty of 1956, in force 1962). The ceding State cannot give more rights than it has.

(5) Subjugation or conquest. Acquisition by force followed by annexation. Once a valid mode, it is now unlawful: Article 2(4) of the Charter; the Friendly Relations Declaration, 1970 (no territorial acquisition resulting from the threat or use of force shall be recognised as legal); Security Council Resolution 662 (1990) declared Iraq's annexation of Kuwait null and void. Treaties of cession procured by force are void under Article 52 of the VCLT.

Other ways. Adjudication by a tribunal (the Rann of Kutch award between India and Pakistan, 1968); plebiscite and self-determination; acquiescence and estoppel (below).

3. Temple of Preah Vihear

Temple of Preah Vihear (Cambodia v. Thailand), ICJ, 1962. A Franco-Siamese treaty of 1904 fixed the boundary along the watershed. A map prepared by French officers in 1907 (the Annex I map) placed the temple on the Cambodian side, though the watershed line would have put it in Thailand. Siam received the map and did not object; in 1930 Prince Damrong, a senior Siamese official, visited the temple and was received by the French in a way that implied French sovereignty, and still Siam did not protest. The Court held that Thailand, by its conduct over some fifty years, had accepted the map line and was precluded from denying it. The temple was in Cambodian territory; Thailand had to withdraw its forces and return objects removed. In 2013, interpreting the judgment, the Court held that Cambodia had sovereignty over the whole promontory of Preah Vihear.

Principles: acquiescence (qui tacet consentire videtur si loqui debuisset ac potuisset: he who keeps silent is held to consent if he ought to have spoken and was able to); stability of boundaries.

4. Restrictions on territorial sovereignty

• Condominium: joint sovereignty of two States (the Anglo-French New Hebrides, 1906–1980).
• Leased territories: Hong Kong's New Territories leased to Britain for 99 years (1898); the Tin Bigha corridor leased by India to Bangladesh in perpetuity.
• International servitudes: rights in favour of another State over a territory, such as rights of passage or fishing (Right of Passage over Indian Territory, Portugal v. India, ICJ, 1960).
• Demilitarisation and neutralisation by treaty (the Åland Islands).
• Treaty restrictions such as limits on alienation, and general limits: diplomatic immunities, innocent passage, and the duty not to cause harm to neighbours (Trail Smelter; Corfu Channel).

5. Loss of territory

The converse of acquisition: cession, dereliction (abandonment with intent to abandon), operation of nature (erosion), prescription in favour of another State, subjugation (historically), and revolt or secession leading to a new State (Bangladesh, 1971). Decolonisation is the largest example; in the Chagos advisory opinion (ICJ, 2019) the Court held that the detachment of the Chagos Archipelago from Mauritius in 1965, before Mauritian independence, was not based on the free and genuine will of the people, so the decolonisation of Mauritius was not lawfully completed, and the UK was under an obligation to end its administration of the archipelago as rapidly as possible. The UK and Mauritius signed a treaty on 22 May 2025 recognising Mauritian sovereignty, with Diego Garcia leased back to the UK; as of the most recent reports I can confirm (April 2026), it had not been ratified by the UK or entered into force.

6. Cession and the Indian Constitution

• In re Berubari Union and Exchange of Enclaves, 1960 INSC 49, AIR 1960 SC 845. Implementing the Nehru-Noon Agreement of 1958, which ceded part of Berubari to Pakistan, required a constitutional amendment under Article 368, not merely a law under Article 3. The Ninth Amendment, 1960, followed.
• Maganbhai Ishwarbhai Patel v. Union of India, 1969 INSC 4, (1970) 3 SCC 400. Settling an undefined boundary (the Rann of Kutch award) is not cession, so no amendment was needed.
• Union of India v. Sukumar Sengupta, 1990 INSC 177. The lease of the Tin Bigha corridor to Bangladesh did not amount to cession, since India retained sovereignty, so no constitutional amendment was required.

7. Problem: discovery against effective control

State H claims sovereignty over an island on the ground that it discovered it, but has no effective sovereignty over it. State N claims the island on the ground that it has had effective control and sovereignty over it for the last three hundred years. Which State has sovereignty? (February 2025)

Issue. Whether a title based on discovery prevails over a title based on long, continuous and effective display of State authority.

Law. Discovery creates only an inchoate title, which must be perfected by effective occupation within a reasonable time. Sovereignty is established by the continuous and peaceful display of State functions (Island of Palmas, 1928). Where the original holder fails to protest against another State's long and open exercise of authority, it is taken to have acquiesced (Temple of Preah Vihear, 1962), and the other may acquire title by prescription (Minquiers and Ecrehos, 1953).

Application. H has done nothing beyond discovery: no administration, no settlement, no exercise of jurisdiction. Its inchoate title lapsed for want of effective occupation. N has displayed authority over the island for three centuries, and nothing suggests H protested. These are the facts of Palmas, with H in the position of Spain (and the US as its successor) and N in the position of the Netherlands.

Conclusion. N has sovereignty. If the facts showed that N's control began by force after 1945, or that H had protested consistently, the answer would need to be qualified, since force cannot found title today and protest prevents prescription.

Variant (April 2023): H claims by continuous exercise of sovereignty with intent to rule; N claims under a treaty with State A, whose colony the island was. The answer turns on nemo dat: A could cede only what it had. If H's continuous display of authority had already given it title before the treaty (or A had lost title by acquiescence), N acquires nothing; this is again Palmas, where the US took by the Treaty of Paris (1898) only such rights as Spain had, and Spain no longer had title.

How this is examined

The modes essay is answered with each mode defined, its requirements, and one case each, ending with the illegality of conquest. A short note on Preah Vihear needs the 1904 treaty, the 1907 map, Prince Damrong's 1930 visit, the 1962 holding on acquiescence and the 2013 interpretation. The island problem appears every second year in some form; answer it as above, naming Palmas.