A number of methods of acquisition of sovereignty are presently or have historically been recognised by international law as lawful methods by which a state may acquire sovereignty over territory.

Accretion

Accretion refers to the physical expansion of an existing territory through geographical 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. Examples of cession include the cession of Hong Kong and Kowloon, purchases such as the Louisiana Purchase and the Alaska Purchase, and cessions involving multiple parties such as the Treaty on the Final Settlement with Respect to Germany.

Since the emergence of self-determination as a recognised principle of international law, a state may need to consult the inhabitants of a territory (if any) before they may cede sovereignty over it.

Conquest

Conquest, the acquisition of territory by way of force, was historically recognised as a lawful method for acquiring sovereignty, but has been illegal in international law at least since the entry into force of the United Nations Charter.

Occupation

Occupation is the effective control of territory exercised by a power with no sovereign title to the land, whether in defiance or absence of a proper sovereign.^[1]

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.

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