Unlike a treaty agreement, customary international law is usually not written. Customs of a longstanding nature can be codified by formal treaties. The Laws and Customs of War on Land (Hague Convention IV)

Many provisions of international law are based upon principles and norms that were developed in the Americas during the 19th century. They include

Sovereign states have the right to defend themselves against overt external aggression, in the form of an invasion or other attack. A number of

See related article Israeli West Bank barrier.
Israel has completed long stretches of barriers within the West Bank, separating Israel proper, Israeli settlements and large parts of the Palestinian territories from Palestinian cities and

In their relations with other peoples and countries during the colonial era the Concert of Europe adopted a fundamental legal principle that the

The Geneva Conventions and other international tractates recognize that land: a) conquered in the course of a war; and b) the disposition of which is

Legal definition of refugee
The tractate that is most often invoked for legally defining refugees is the 1951 Convention Relating to the Status of Refugees