The following are the modes of acquisition of territory: In International Law a territory may be acquired by the following means:-
1. Occupation: – occupation in International Law means an act of appropriation by a State over a territory which does not belong to any other State. Such territory may be uninhabited such as an island, or may be inhabited by persons whose community is not considered as a State.
b) the State acquiring territory should take the corpus i.e., possession.
2. by annexation – annexation is meant the forcible acquisition of territory by one State at the expense of another. When a State annexes the territory-either entire territory or a part of it, it establishes its sovereignty over the annexed territory. In contrast to other methods of acquiring territorial sovereignty or acquisition by an international legal transaction, the element of force plays a decisive role. Annexation can take place in two ways:
• By an Unilateral Declaration. -After the conquest or the territory in question and the final defeat of the adversary when a declaration of annexation made by a State wherein it announces its intention or acquiring territorial Sovereignty over the area in question, annexation is said to have taken place.
• By the Treaty.- Unlike other treaties concerning territorial changes, there must be an element of compulsion. This means that the ceding State has either been forced to sign a peace treaty after a military defeat or persuaded to agree by non-military means.
After the establishment of the United Nations, acquisition of territory through annexation has become illegal under Article 2, Para 4. acquisition of territory resulting from threat or use of force if it is not inconsistent with the purposes of the United Nations will not be regarded as an illegal acquisition. For instance, a State that actsin self-defence to repel armed force used against it contrary to Article 2(4) can acquire any territory of the aggressor which it occupies during hostilities.
2. Accretion:-A territory by accretion may be obtained by a State. Sometimes by natural calamities also a territory comes within the jurisdiction of a State through the same was previously a portion of another State. For this here is no need of any formal action or declaration.
3. Prescription: – By prescription a territory comes within a State when by continuous occupation and control of that territory for a long time creates a vested authority in the controlling State and by passage of time that State becomes the actual and real sovereign over that territory. As to length of time for the acquisition of territory through prescription it is submitted that no general rule can be laid down. Length of time may be different depending upon the circumstances and nature of the territory from case to case.
4. Cession: – By cession also a territory comes within the authority of a State. The cession may occur as a result of a war through pressure or it may be voluntary. The Cession will be valid only when the sovereignty over the territory is transferred from one state to another with the territory while in accretion only one party may act. Under article 368, Parliament may make a law to give effect to an implement the agreement in question covering Cession of a part of Berubari Union NO.12 as well as some of the Cooch-Behar Enclaves.
5. Conquest: When a state gets victory over the other State then the sovereignty over the conquered state is not established only by victory. For sovereignty it is necessary that the victor State establishes an effective authority over the territory of the conquered state through annexation. The importance of this means is more or less extinct because of the Charter of the U.N.O. by which intervention of one state on the affairs of another is prohibited.
6. Lease: – The territory may also be acquired through lease. A state may give its territory o another state under lease for a certain period. For the said certain period some rights of sovereignty are transferred to another. A good example of this type of lease is transfer of certain Islands on lease by Malta to Great Britain for some years. Recently India had also leased three Bigha to Bangladesh. Case Union of India v/s Sukumar Sengupta-1990, it was held that the concessions given to Bangladesh over the said area amounted to servitude.
7. Pledge:-Sometimes there arise certain circumstances under which a State becomes compelled to pledge a part of its territory in return of some amount of money for which it is in dire need. In this case also a part of sovereignty over the territory concerned is transferred. For example in 1768 the Republic of Geneva had pledged the Island of Corsica to France.
8. Plebiscite:-Some writers of the view that through plebiscite also new State may be acquired.
9. Through Independence obtaining of territorial sovereignty:-those States which were colonies after attaining independence get sovereignty over the territory which consisted within the colonial setup.
10. Award – Territory may also be acquired by a State through adjudication by a judicial organ such as international court of justice , ad hoc arbitral tribunals or conciliation commissions.