Territory is considered "occupied" when it is actually placed under the authority of foreign armed forces, whether partially or entirely, without the consent of the domestic government. The occupation extends only to the territory where such authority has been established and can be exercised.

International humanitarian law (IHL) applies in all situations where these requirements are fulfilled, regardless of the reasons and motives that lead to the occupation (e.g. stated intention to "liberate" the people of a country) and regardless of its legality under international law.

The primary sources of the modern law of occupation are the Hague Regulations of 1907, the Fourth Geneva Convention of 1949 and certain provisions of the First Protocol of 1977 Additional to the Geneva Conventions of 1949.

A situation of occupation confers both rights and obligations on an occupying power. However, while a situation of occupation may in fact prevent a government from exercising sovereignty over part or all of its territory, this does not confer sovereign rights on the occupant. Occupation is by definition a temporary situation that interferes with, but does not diminish or terminate, the sovereign rights of the people under occupation.

Once an occupant has established effective control over a territory it must, as far as possible, restore and maintain public order and safety, while respecting, unless absolutely prevented, the laws in force in the occupied territory.

In addition to the rules found in international humanitarian law, the occupying power must respect human rights law and national law, subject to certain exceptions.

See also:

Civilians in the power of the enemy and international humanitarian law