International Law is based on the concept of the State. No State can exist without territory. International disputes pertaining to land title as well as the precise determination of State boundaries, are the subject of international proceedings.[1] As you know that, international community comprises of States, and the existence of the States are defined by their territory and sovereignty. The sovereignty sits at heart of the International Law.

In International Community, all States possess territory - although there are examples of 'micro-states' i.e., the Holy see.[2] The Sovereign Military Hospitaller Order of St John of Jerusalem of Rhodes and of Malta also known as the Sovereign Order of Malta, claims statehood but no longer possesses territory. In 1978, the Order was ousted from its last surviving possession. Afterward, it has occupied certain areas of Rome. In fact, the few States recognize the Order, therefore it is State with no territory.

Territory refers to a geographical concept. Land, rivers, lakes, roofs, islands, internal or international waters, territorial space, and air space are all included in it. Territory can be subject to one of four types of regimes, one of which is territorial sovereignty.

They are as follows:

• Res nullius:
  Territory may be acquired by the States, but it has not yet been granted territorial sovereignty.
   
• Res communis:
  Territory that cannot be governed by a state such as the high seas and the exclusive economic zones.
   
• Terra nullius:
  Territory that has never belonged to any other State, but these States have their own status. [3]

The title to territory is based on sovereignty. So, it is necessary to discuss about the territorial sovereignty in brief. In Islands of Palma Case, Judge Huber observed:
Sovereignty in relation between the states signifies independence. Independence in regard to portion of the globe is their right to exercise therein, to the exclusion of any other state, the functions of a state.[4]

Therefore, State exercises its supreme authority within its territory. The territorial sovereignty enables a State to exercise its fullest measure of sovereignty powers over its land territory. In order to function as State, the State must possess territory.

Modes Of Acquisition Of State Territory
Traditionally there are several distinct modes by which sovereignty can be acquired over territory. It is now generally acknowledged that these categories are deficient in many aspects. The classification of these modes was originally borrowed from Roman law rules relating to the acquisition of land by private parties. The modes of acquisition are cession, effective occupation, accretion, conquest or subjugation and prescription.

These modes of acquisition can be divided into categories:

1. Original and
2. Derivative.

Occupation and accretion are commonly described as original, cession as derivative. Here, it is pertinent to note that there are still differences of opinion in regard to conquest and prescription. The said classification has no practical value and misleading in terms of modern practice. However, these modes of acquisition of territory fully relevant for two simple reasons.[5]

These are:

1. The Doctrine of inter-temporal demands that a State titles to territory can be judged in the context of the law of time;
2. The modern practice has evolved out of traditional practice, hence 'the old is necessary to an understanding of the new.

Cession
Cession is transfer of territory from one State to another State. The cession of territory means the renunciation made by one State in favor of the rights and title which the former may have to the territory in question.[6] It has often taken place within the framework of treaty either in peaceful or postwar situations. In order to effect cession of territory, it must be clear that transfer of actual sovereignty is intended. Cession without intention cannot legally operate.

It is important to note that State receiving the territory may cede any part of its land territory. By doing this, all its State territory will completely merge with other State. In case of defects in the ceding State's title, the title of the State to which the territory is ceded will be vitiated by same defects.[7]

It is expressed by the Latin maxim, Nemo Dat Quod Non Habet i.e., nobody can give what he doesn't have. It means that acquiring State cannot possess more rights over the territory than its predecessor State had. For this we need to discuss the Island of Palmas[8] case, where the Spain had ceded Philippine Island to the United States by Treaty of Paris concluded in 1898.

The treaty expressed the Island of Palmas as part of the Philippines. When the United States proceeded to take possession of the Island, it found that it was under the control of Dutch. The United States and Netherland referred their dispute to arbitration by sole of arbitrator. The claim of the United States was partly based on Treat of Paris 1898, which transferred all rights over territory to the United States and therefore, the United States had acquired it by way of cession.

On other hand, the Netherlands Government argued that the fact by the discovery of Spain was not proved, and the Netherland possessed and exercised rights of sovereignty for more than 200 years. The arbitrator, Max Huber, held that the treaty could not be regarded as conclusive, the Netherland had administered it since early eighteenth century, it is evident that Spain could not transfer more rights than it itself possessed.

Sometime the cession is an outcome of peaceful negotiation or war. These are some notable examples of peaceful cession in the international legal history: in exchange for Island of Zanzibar, Britain ceded the Island of Heligoland in the North Sea to Germany in 1980; in 1957, the Australia acquired the territory of Christmas Island; Russia ceded its territory of Alaska to the United States for US $ 7.2 million in 1867. It can also be accomplished by gift or voluntary merger of territory. For example, Austria ceded Venice to France as gift in 1866 and later France ceded Venice within a few weeks to Italy.

Occupation
Occupation is the acquisition of terra nullius - that is when a State intentionally acquired sovereignty over territory, belonged to no State.

According to Article 42 of The Hague Regulations of 1907, occupation read as follows:
Territory is considered occupied when it is actually placed under the authority of the hostile army. The occupation extends only to the territory where such authority has been established and can be exercised.

Robert Jennings defines occupation:
The appropriation by a State of territory which is not at time subject to the sovereignty of other State.[9]

The territory in question may have never belonged to any State whether it is uninhabited or inhabited by natives living under tribal organization is not considered to be State. In another scenario, the territory may have been abandoned by previous sovereign. Abandonment of territory means intention to abandon the territory.

In Western Sahara Case,[10] the court prepared an advisory opinion at the request of United Nation on the Western Sahara. The question before the court was whether the western was, at the time of its colonization by Spain, a territory belonged to no one, or terra nullius. In its opinion the Court clearly stated that territory inhabited by the people with political or social structure is not terra nullius.

Therefore, it cannot be occupied.
Territory is occupied when it is placed under effective administrative control. To constitute an effective occupation, the acquiring State must take possession of territory with intention acquiring sovereignty over it. After acquiring possession over territory, the State has to be established an effective administrative system within a reasonable period of time. If the State has failed to establish some responsibility over it, it would not be considered as an effective occupation.

In the Eastern Greenland case,[11] the International Court of Justice noted:
Another circumstance which must be taken into account � is the extent to which the sovereignty is also claimed by some other Power. In the vast majority of instances involving territorial sovereignty claims before an international tribunal, there have been two opposing claims to sovereignty, and the tribunal must decide which is the stronger... in several situations, the tribunal has been comfortable with very little in the way of genuine sovereign powers exercise, as long as the opposing State could not establish a superior claim. This is particularly true in the case of claim to sovereignty over areas in thinly populated or unsettled countries.

In another case,[12] the arbitrator held that in order to acquire territory by occupation there must be:

1. Intention and will to act as sovereign
2. Adequate exercise or display of sovereignty.

Today, there are hardly any parts of the world that could be considered as terra nullius because no terra nullius lands remain on this planet.

Prescription
Prescription is also based on effective control over territory. It may be defined as:
Tthe means by which, under international law, legal recognition is given to the right of a state to exercise sovereignty over land or sea territory in cases where that state has, in fact, exercised its authority in a continuous, uninterrupted and peaceful manner over the area concerned for a sufficient period of time.[13]

No rules laid down that set out minimum times or requisite acts of sovereignty to create such title by prescription. The matter depends upon circumstances of each case. In order to establish title by prescription, there must be effective control, and that control must be for longer period of time. When State acquires territorial sovereignty over another state by way of prescription, it needs to be accompanied by acquiescence on the part of losing State or if the protests, acts or statements of other States demonstrate lack of acquiesce, it may prevent acquisition of title by prescription.

For instance, in Island of Palmas Case,[14] Judge Huber stressed on absence of Spanish protest against Dutch acts on Island.

Now we shall discuss the difference between prescription and acquisition: Prescription is acquisition of territory belonged to another State, whereas the occupation is acquisition of terra nullius. But the difference is usually blurred in real life. In respect of this, the judgment of Island of Palma Case, does not make it clear that whether the island was under Spanish sovereignty or not. In some cases, the international tribunals often decide the cases on the basis of greater degree of effective control over the disputed territory.

For example, in the Eastern Greenland Case,[15] the Permanent Court of International Justice gave judgment in favour of the Denmark due to exercised greater degree of effective control over the territory of Eastern Greenland.[16]

Accretion
Accretion refers to the natural geographical processes that results in an increase or decrease in the territory (physical expansion of territory) due to natural formation of land. It results in new formation of land. New formation may be natural or artificial i.e., outcome of the human work. Artificial formations include man-made islands, embankments, dikes, breakwaters and so on along the coast -line of the sea.

For example, in 2003 Malaysia sought provisional measures against Singapore for the international tribunal of law of the sea in relation to concern over environmental impacts from proposed land reclamation works in the Straits of Johor. Natural Formations include lands formed due to volcanic actions, the abandonment of a river channel and the formation of new channel, the drying up and change in the course of boundary river or the gradual deposits of materials in river deltas.[17]

In case of a drying or shifting of a boundary river:

1. If the change is gradual or slight, the boundary may be shifted;
2. If the change is violent and excessive, the boundary remains at the same position along the previous riverbed.

No State is allowed to alter the natural conditions of its own territory to the disadvantage of the natural conditions of a neighbouring State territory without a previous agreement with the neighbouring States.

For Instance, the Island of Surtsey was formed due to volcanic eruption, and the Island was acquired by Iceland in 1963. In addition to this, Australia's McDonald Island appears to have grown in terms of geographical area due to volcanic eruption. It is crystal clear, that in future, Australia will have sovereignty over the newly formed areas.

Chamizal Case:[18] In instant case, there was a border conflict between the United States and Mexico. The Rio Grande River is the part of boundary between the United States and Mexico, which was set out as boundary between in 1848. The Rio Grande had shifted towards southward in 1911. Around 600 acres of territory (Chamizal Tract) south of the old river bed was now north of the new course of river. It was held by arbitrators that the Chamizal Tract was now part of the United States.

Subjugation
Subjugation is the mode of acquisition of territory by conquest followed by annexation. In those days acquisition of territory by conquest was not lawful until the defeated State entered into a peace treaty which ceded territory to the victor or which recognized the victor's title. In case of absence of peace treaty, it was necessary to show that war had come an end by way of producing evidence. For Instance, German annexation of Poland during Second world war was invalid due to continued struggle against Germany by Poland allies.

Treaty by way of aggression or force is void under International Law. In February 1932, Japan troops created a puppet state of Manchukuo. Almost all States called for strict implementation of the covenant.

After long negotiations, the assembly of the League of Nations passed a resolution stating that:
It is incumbent upon the members of the League of Nations not to recognize of any situation, treaty or agreement which may be brought about by means contrary to the Covenant of the League of Nations.

Article 10 of the League of Nations Covenant provides:
The Members of the League undertake to respect and preserve as against external aggression the territorial integrity and existing political independence of all Members of the League. In case of any such aggression or in case of any threat or danger of such aggression the Council shall advise upon the means by which this obligation shall be fulfilled.[19]

Therefore, it is illegal to wage war against another State for the purpose of acquiring territory. It also casts duty upon the States to respect the territorial integrity of their neighboring States as well as other States.

The said principle is reiterated in the 1970 General Assembly:
Declaration on Principles of International Law Concerning Friendly Relations and Co-operation among States in Accordance with the Charter of the United Nations.[20]

It provides:
The territory of a State shall not be object of military occupation resulting from the use of force. In contravention of the provisions of the Charter. The territory of a State shall not be the object of acquisition by another State resulting from the threat or use of force.

The annexation of Kuwait by Iraq is another example of annexation. Iraq accused Kuwait of stealing oil through slant drilling. On Aug 02, 1990, Iraqi forces invaded oil-rich country Kuwait. In response to this, United Nations Security Council unanimously declared the annexation null and void and called upon states and institutions not to recognize it.[21]

Loss Of State Territory
Now we can easily identify the corresponding method of losing State territory. The modes are cession, dereliction, operation of nature, subjugation, prescription and revolt. We have already discussed loss of territory by way of subjugation, prescription and cession. Revolt is one of the only modes of loss of territory in which there is no corresponding mode of acquisition. However, it appears that revolt is more about political matter rather than a legal mode of loss of territorial sovereignty.

For Instance, the revolt of the Spanish Netherlands results in collapse of Spain. On other hand operation of Nature as mode of losing territory corresponds to Accretion. The difference between accretion operation of nature is that former results in extension of territory whereas, latter results in disappearance of territory due to natural calamities. Now we shall discuss the last mode i.e., dereliction. Dereliction corresponds to the occupation. It simple means abandonment and relinquishment of territorial sovereignty. There must be actual abandonment of territory and also an intention of giving up sovereignty.

Conclusion
We've learned about the importance of territory for a state's existence, and how a state exercises sovereignty over its territory. We also highlighted the numerous processes through which governments acquire and lose territory. The mode of acquisition of territory in international is highly difficult and impossible. In modern international law, the only legal way to acquire the territorial sovereignty is by way of treaty. The legality or illegality of such conduct should be evaluated on the basis of applicable law. Peaceful resolution of territorial disputes results in international peace.

End-Notes:

1. Bay of Bengal Maritime Boundary Arbitration (Bangladesh v India) (2014) 167 ILR 1
2. Donald R Rothwell, Stuart Kaye, et.al., International Law Cases and materials with American perspectives Chapter 6 (Cambridge University Press, 8th edn., 2018)
3. Gideon Boas, Public International Law Contemporary Principles and Perspectives Chapter 4 at 4.6.1 (Edward Elgar Publishing Limited, 2012)
4. Island of Palma Case (The Netherland vs United States) (1928) 2 RIAA 829, 838.
5. See Supra note 3 Chapter 4 at 4.6.4.
6. Annual Digest of International Law Case (Reparation Commission v. German Government) (1924) 199.
7. Peter Malanczuk, Akehurst's Modern Introduction to International Law Chapter 10 (Taylor and Francis, 7th edn., 2002).
8. See Supra note 4.
9. Randall Lesaffer, Argument from Roman Law in Current International Law: Occupation and Acquisitive Prescription Vol 16 no. 1 The European Journal of International Law 25-58 (2005).
10. Western Sahara (Advisory Opinion) (1975) ICJ 12.
11. Legal Status of Eastern Greenland (Denmark v. Norway) (1933) PCIJ.
12. Clipperton Island Case (France v Mexico) (1932) RIAA 1105.
13. See Supra note 3.
14. Island of Palma Case (The Netherland vs United States) (1928) 2 RIAA 829, 838.
15. Legal Status of Eastern Greenland (Denmark v. Norway) (1933) PCIJ.
16. Peter Malanczuk, Akehurst's Modern Introduction to International Law Chapter 10 p. 151 (Taylor and Francis, 7th edn., 2002).
17. Donald R Rothwell, Stuart Kaye, et.al., International Law Cases and materials with American perspectives Chapter 6 (Cambridge University Press, 8th edn., 2018)
18. United Nations, Report of International Arbitral Awards; The Chamizal Case (Mexico, United States) (1911) Vol. XI pp. 309-347 available at https://www.internationalwaterlaw.org/cases/Chamizal_Arbitration.pdf
19. Available at https://www.ungeneva.org/en/covenant-lon
20. Available at http://hrlibrary.umn.edu/instree/principles1970.html
21. Resolution 660 (1990), Adopted by the Security Council at its 2932nd meeting, on 2 August 1990, Available at https://digitallibrary.un.org/record/94220?ln=en