Uti possidetis

In the early 17th century, the term was used by England's James I to state that while he recognized the existence of Spanish authority in the regions of the Western Hemisphere in which Spain exercised effective control, he refused to recognize Spanish claims to exclusive possession of all territory west of longitude 46° 37' W under the Treaty of Tordesillas.

More recently, the principle has been used in the modified form uti possidetis juris to establish the frontiers of the newly independent states by ensuring that the frontiers followed the original boundaries of the old territorial entities from which they emerged. The newly formulated principle has been applied in numerous regions, such as South America, Africa, Yugoslavia, and Soviet Union, in which central governments were dissolved, or after decolonization, the end of a mandate, or the overthrow of imperial rulers. That use originated in South America in the 19th century with the withdrawal of the Spanish Empire.[2] By declaring that uti possidetis applied, the new states sought to ensure that there was no terra nullius in South America when the Spanish withdrew and to reduce the likelihood of border wars between the newly independent states and the establishment of new European colonies.

The same principle was applied to Africa and Asia after the withdrawal of European powers from those continents and in locations such as the Soviet Union whose former central governments fell and constituent states gained independence. In 1964, the Organisation of African Unity passed a resolution stating that the principle of stability of borders, the key principle of uti possidetis, would be applied across the continent. Most of Africa was already independent and so the resolution was principally a political directive to settle disputes by treaty based on pre-existing borders, rather than by resorting to force. To date, adherence to the principle has allowed African countries to avoid border wars; the notable exception, the Eritrean–Ethiopian War of 1998–2000, had its roots in a secession from an independent African country, rather than a conflict between decolonized neighbours.[3] On the other hand, the colonial boundaries often did not follow ethnic lines, which has contributed to violent and bloody civil wars among differing ethnic groups in many postcolonial (and postcommunist) countries, including Sudan, the Democratic Republic of the Congo, Angola, Nigeria, Uganda, Georgia, Azerbaijan, Moldova and the former Yugoslavia.[4]

The principle was affirmed by the International Court of Justice in the 1986 case Burkina-Faso v Mali:

[Uti possidetis] is a general principle, which is logically connected with the phenomenon of obtaining independence, wherever it occurs. Its obvious purpose is to prevent the independence and stability of new states being endangered by fratricidal struggles provoked by the changing of frontiers following the withdrawal of the administering power.

• De facto
• Ex factis jus oritur
• Facts on the ground
• Fait accompli
• Revanchism
• Status quo ante bellum

• Lecture by Marcelo Kohen entitled "Uti Possidetis and Maritime Delimitations" in the Lecture Series of the United Nations Audiovisual Library of International Law

• Sebastian Anstis and Mark Zacher (June 2010). "The Normative Bases of the Global Territorial Order." Diplomacy and Statecraft 21: 306–323.
• Helen Ghebrewebet: "Identifying Units of Statehood and Determining International Boundaries: A Revised Look at the Doctrine of Uti Possidetis and the Principle of Self-Determination", Verlag Peter Lang 2006, ISBN 3-631-55092-8.