A number of methods of acquisition of sovereignty are or have been recognised by

international law International law (also known as public international law and the law of nations) is the set of rules, norms, and standards generally recognized as binding between states. It establishes normative guidelines and a common conceptual framework for ...

as lawful methods by which a state may acquire

sovereignty Sovereignty is the defining authority within individual consciousness, social construct, or territory. Sovereignty entails hierarchy within the state, as well as external autonomy for states. In any state, sovereignty is assigned to the perso ...

over

territory A territory is an area of land, sea, or space, particularly belonging or connected to a country, person, or animal. In international politics, a territory is usually either the total area from which a state may extract power resources or a ...

. International law adopts much of Roman property law in regards to acquisition of sovereignty due to the underlying European civil law at the time of early discovery voyages such as

Christopher Columbus Christopher Columbus * lij, Cristoffa C(or)ombo * es, link=no, Cristóbal Colón * pt, Cristóvão Colombo * ca, Cristòfor (or ) * la, Christophorus Columbus. (; born between 25 August and 31 October 1451, died 20 May 1506) was a ...

. The basis of acquisition of states ownership of vacant territory therefore continues to apply, (and was often applied historically to land already possessed by

indigenous populations Indigenous peoples are culturally distinct ethnic groups whose members are directly descended from the earliest known inhabitants of a particular geographic region and, to some extent, maintain the language and culture of those original people ...

Accretion

Accretion refers to the physical expansion of an existing territory through geological processes, such as alluvion (the deposit of sediment) or vulcanism.

Cession

A state may acquire sovereignty over territory if that sovereignty is ceded (transferred) to it by another state. Cession is typically effected by

treaty A treaty is a formal, legally binding written agreement between actors in international law. It is usually made by and between sovereign states, but can include international organizations, individuals, business entities, and other legal per ...

. Examples of cession include the cession of Hong Kong Island and Kowloon, purchases such as the

Louisiana Purchase The Louisiana Purchase (french: Vente de la Louisiane, translation=Sale of Louisiana) was the acquisition of the territory of Louisiana by the United States from the French First Republic in 1803. In return for fifteen million dollars, or ap ...

and the Alaska Purchase, and cessions involving multiple parties such as the Treaty on the Final Settlement with Respect to Germany.

Conquest

Direct annexation, the acquisition of territory by way of force, was historically recognized as a lawful method for gaining sovereignty over newly acquired territory. By the end of

World War II World War II or the Second World War, often abbreviated as WWII or WW2, was a world war that lasted from 1939 to 1945. It involved the World War II by country, vast majority of the world's countries—including all of the great power ...

, however, invasion and annexation ceased to be recognized by international law and were no longer accepted as a means of territorial acquisition. The Convention respecting the Laws and Customs of War on Land (Hague IV, 1907) contains explicit provisions concerning the protection of

civilian Civilians under international humanitarian law are "persons who are not members of the armed forces" and they are not " combatants if they carry arms openly and respect the laws and customs of war". It is slightly different from a non-combatant ...

s and their property in

occupied territories Military occupation, also known as belligerent occupation or simply occupation, is the effective military control by a ruling power over a territory that is outside of that power's sovereign territory.Eyāl Benveniśtî. The international law ...

. The

United Nations Charter The Charter of the United Nations (UN) is the foundational treaty of the UN, an intergovernmental organization. It establishes the purposes, governing structure, and overall framework of the United Nations System, UN system, including its Organ ...

also has related provisions regarding territorial integrity. In the case of ''United States v. Huckabee'' (1872), the

United States Supreme Court The Supreme Court of the United States (SCOTUS) is the highest court in the federal judiciary of the United States. It has ultimate appellate jurisdiction over all U.S. federal court cases, and over state court cases that involve a point o ...

, speaking through Justice Nathan Clifford, said: "Power to acquire territory either by conquest or treaty is vested by the Constitution in the United States. Conquered territory, however, is usually held as a mere military occupation until the fate of the nation from which it is conquered is determined ... ".

Effective occupation

Effective occupation is the control of free newly discovered territory exercised by a power with no sovereign title to the land, whether in defiance or absence of a proper sovereign. Several cases in international law have dealt with what "effective occupation" entails. In the words of the Eritrea/Yemen Arbitration Award: Also in the case of Mexico and France over Clipperton Island: In the case of the Netherlands and the United States in the Island of Palmas case, the arbitrator ruled:

Prescription

Prescription is related to occupation, and refers to the acquisition of sovereignty by way of the actual exercise of sovereignty, maintained for a reasonable period of time, that is effected without objection from other states and countries.

Accretion

Cession

Conquest

Effective occupation

Prescription

References

Other readings