Condominium (international law)

In international law, a condominium (plural either condominia, as in Latin, or condominiums) is a political territory (state or border area) in or over which two or more sovereign powers formally agree to share equally dominium (in the sense of sovereignty) and exercise their rights jointly, without dividing it up into 'national' zones.

Although a condominium has always been recognized as a theoretical possibility, condominia have been rare in practice. A major problem, and the reason why so few have existed in practice, is the difficulty of ensuring co-operation between the sovereign powers; once the understanding fails, the status is likely to become untenable.

The word is recorded in English since c. 1714, from Modern Latin, apparently coined in Germany c. 1700 from Latin com- "together" + dominium "right of ownership" (compare domain).

Current condominia

 * The Moselle River, and its tributaries the Sauer and the Our, comprise a condominium between Luxembourg and Germany, who share bridges and at least the tip of one island, Staustufe Apach, near Schengen (the rest of the island is in France). The condominium was established by treaty in 1816.
 * Pheasant Island (also known as Conference Island, Konpantzia in Basque, Île de la Conférence in French or Isla de los Faisanes in Spanish) in the River Bidassoa between France and Spain. It was established by the Treaty of the Pyrenees in 1659.
 * A small area (Hadf and surroundings) on the Arabian Peninsula is jointly ruled by Oman and the Emirati member state of Ajman.
 * Parts of the Gulf of Fonseca and of the territorial sea outside its mouth comprise a unique tridominium between El Salvador, Honduras and Nicaragua.
 * The main part of Lake Constance (without islands) is considered by Austria and Germany to be a tridominium between Germany, Austria and Switzerland (albeit on different grounds), while Switzerland holds the view that the border runs through the middle of the lake. Hence no international treaty establishes where the borders of Switzerland, Germany, and Austria in or around Lake Constance lie.
 * The part of the Paraná River between the Salto Grande de Sete Quedas and the mouth of the Iguassu River is shared in condominium by Brazil and Paraguay.
 * Brčko District of Bosnia and Herzegovina forms part of both the Republika Srpska and the Federation of Bosnia and Herzegovina.
 * Jamaica and Colombia share a maritime condominium (called a "Joint Regime Area") by mutual agreement as an alternative to delimiting their sea boundary. The outer portion of the EEZ of each country otherwise would overlap in this area.  Unlike other "joint development zones," this condominium appears not to have been purposed simply as a way to divide oil, fisheries or other resources.

Co-principality
Under French law, Andorra was once considered to be a French–Spanish condominium, although it is more commonly classed as a co-principality, since it is itself a sovereign state, not a possession of one or more foreign powers, even though the quality of Head of State is shared ex officio by two foreigners, one of which being the President of France, currently François Hollande.

Former condominia

 * In 688 the Byzantine Emperor Justinian II and the Arab Caliph Abd al-Malik ibn Marwan reached an unprecedented agreement to establish a condominium (the  concept did not yet exist) over Cyprus, with the collected taxes from the island being equally divided between the two parties. The arrangement lasted for some 300 years, despite the fact that in the same time there  was nearly constant warfare between the two parties on the mainland.
 * In the early 9th century, Serbian princedom was a condominium of Frankish Empire and Byzantine Empire.
 * Anglo-Egyptian Sudan was legally an Egyptian-British condominium from 1899 until 1956, although in reality Egypt played no role in its government other than providing some administrators in the country, all political decisions were made by the UK and all Governors-General of the Anglo-Egyptian Sudan were British. Though the system was resented by Egyptian and Sudanese nationalists, and would later be disavowed by the Egyptian Government, it persisted due to the United Kingdom's effective control over Egypt itself, which began from 1882 and continued until at least 1936.
 * Bosnia and Herzegovina was a condominium of Cisleithanian Austria and Hungary between 1908 and 1918, while both countries were parts of the Austro-Hungarian Empire.
 * An islet in the border river Brömsebäck was considered to belong to neither (or both) Denmark and Sweden.
 * The Independent State of Croatia during World War II from 1941 to 1943 was a condominium of Nazi Germany and Fascist Italy until the collapse of the Italian Fascist regime in 1943.
 * Canton and Enderbury Islands were a British–American condominium from 1939 until 1979 when they became part of Kiribati
 * Couto Misto was shared until 1864 between Spain and Portugal, even though in its final decades of existence it was de facto independent.
 * Countship of Friesland (West Frisia), since 1165 under Imperial administration, was from 1165 to 1493 a joint condominium of the Count of Holland and the Prince-bishop of Utrecht, then again until 25 October 1555 under Imperial administration
 * Egypt from 1876-1882, under France and the United Kingdom.
 * The City of Erfurt from 12th century until the Thirty Years' War was shared between the Archbishopric of Mainz and the Counts of Gleichen, the latter replaced by the city council in 1289 (Concordata Gebhardi), the Landgrave of Thuringia in 1327 and the House of Wettin in 1483 (Treaty of Weimar)
 * The Free City of Kraków was a protectorate of Prussia, Austria and Russia from 1815 until 1846, when it was annexed by Austria
 * Maastricht, was a condominium for five centuries until 1794. It was shared between the Prince-Bishopric of Liège and the Duchy of Brabant, the latter replaced by the Dutch Republic in 1632
 * Nauru a tripartite condominium mandate territory administered by Australia, New Zealand and United Kingdom from 1923 to 1942 and again in 1947 as a trust territory until independence in 1968
 * The village of Nennig was a condominium of the Trier bishopric, Lorraine (the Kingdom of France from 1766) and Luxembourg until its annexation by Revolutionary France in 1794
 * Neutral Moresnet was shared from 1816 until 1919 between the Netherlands (later Belgium) and Prussia
 * New Hebrides formed a French–British condominium in 1906 until independence in 1980 as a republic, now called Vanuatu
 * Northern Dobruja by the Central powers (German-Austrian-Bulgarian) during World War I.
 * Oregon Country was an Anglo-American condominium from 1818 until 1846
 * Samoan Islands from 1889 to 1899 were a rare tripartite condominium under joint protectorate of Germany, Britain and the USA.
 * The Province of Schleswig-Holstein was at first administered jointly by Prussia and Austria following the 1864 Second Schleswig War until its partition according to the Gastein Convention in the next year
 * The County of Sponheim in the Holy Roman Empire was ruled since the 15th century by the Margraves of Baden, the Counts Palatine of the Rhine and the Counts of Veldenz, later Palatinate-Simmern, Palatinate-Zweibrücken and Palatinate-Birkenfeld as heirs of Veldenz.
 * Togoland, formerly a German protectorate, was an Anglo-French condominium, from when the United Kingdom and France occupied it on 26 August 1914 until its partition on 27 December 1916 into French and British zones. The divided Togoland became two separate League of Nations mandates on 20 July 1922: British Togoland, which joined Gold Coast (present day Ghana) in 1956, and French Togoland, which is now the nation of Togo.
 * Zaporozhian Sich, a brief Russo-Polish condominium, was established in 1667 by the Treaty of Andrusovo.
 * The term is sometimes even applied to a similar arrangement between members of a Monarch's countries in (personal or formal) union, as was the case for the district of Fiume (Rijeka), shared between Hungary and Croatia within the Habsburg Empire since 1868.
 * Between 1913 and 1920 Spitsbergen was a neutral condominium. The Spitsbergen Treaty of February 9, 1920, recognises the full and absolute sovereignty of Norway over all the arctic archipelago of Svalbard. The exercise of sovereignty is, however, subject to certain stipulations, and not all Norwegian law applies. Originally limited to nine signatory nations, over 40 are now signatories of the treaty. Citizens of any of the signatory countries may settle in the archipelago. Currently, only Norway and Russia make use of this right.

Proposed condominia

 * In 2001, the British government held discussions with Spain with a view to putting a proposal for joint sovereignty to the people of Gibraltar. This initiative was pre-emptively rejected by Gibraltarians in the 2002 referendum.
 * In 2012, the Canadian and Danish governments were close to an agreement to declare Hans Island a condominium, after decades in dispute. Another considered alternative was to divide the island in half. Negotiations are still in progress.