Condominium (international law)

A condominium (plural either condominia, as in Latin, or condominiums) in international law is a political territory (state or border area) in or over which multiple sovereign powers formally agree to share equal dominium (in the sense of sovereignty) and exercise their rights jointly, without dividing it 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 so few have existed, 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 con- 'together' + dominium 'right of ownership' (compare domain). A condominium of three sovereign powers is sometimes called a tripartite condominium or tridominium.

Current condominia

Abyei Area

The 2005 Comprehensive Peace Agreement, which ended the Second Sudanese Civil War, created a special status administrative area known as the Abyei Area, which is considered to simultaneously be part of West Kordofan state and Northern Bahr el Ghazal state. Following the independence of South Sudan in 2011, the area effectively became a condominium between the Republic of South Sudan and the Republic of the Sudan.


Antarctica is a de facto continental condominium, governed by the 29 parties to the Antarctic Treaty that have consulting status.

Brčko District

In Bosnia and Herzegovina, the Brčko District forms a condominium between the Federation of Bosnia and Herzegovina and Republika Srpska.[1]

Gulf of Fonseca

El Salvador, Honduras, and Nicaragua exercise a tripartite condominium over parts of the Gulf of Fonseca and of the territorial sea outside its mouth.[2][3][4]

Joint Regime Area

As an alternative to delimiting their sea boundary, Colombia and Jamaica share a maritime condominium called the Joint Regime Area in the Caribbean Sea by mutual agreement. 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.

Lake Constance

Austria, Germany, and Switzerland consider themselves to hold a tripartite condominium (albeit on different grounds) over the main part of Lake Constance (without its islands). On the other hand, Switzerland holds the view that the border runs through the middle of the lake.[5][6] Hence, no international treaty establishes where the borders of Switzerland, Germany, and Austria, in or around Lake Constance, lie.[6]


The Moselle and its tributaries, the Sauer and the Our, constitute a condominium between Germany and Luxembourg, which also includes bridges, about 15 river islands of varying size,[7] and the tip of one island, Staustufe Apach,[8] near Schengen (the rest of the island is in France). The condominium was established by treaty in 1816.

Pheasant Island

Pheasant Island (also known as Conference Island, Isla de los Faisanes in Spanish, Île de la Conférence in French or Konpantzia in Basque) in the Bidassoa is a condominium between France and Spain. It was established by the Treaty of the Pyrenees in 1659. It is formally administered by Spain between 1 February and 31 July each year (181 or 182 days) and by France between 1 August and 31 January each year (184 days). The island has no permanent population and has been eroded significantly by the river.[9]


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. However, the position of head of state is shared ex officio by two foreigners, one of whom is the President of France, currently Emmanuel Macron, and the other the Bishop of Urgell in Spain, Joan Enric Vives i Sicília.[10]

Former condominia

Flags of the Anglo-Egyptian Sudan (1899–1956)

Proposed condominia

  • In a 2019 essay, former Australian Prime Minister Kevin Rudd suggested that Australia should consider a "formal constitutional condominium" with Tuvalu, Kiribati, and Nauru as a solution to the impacts of climate change. Rudd outlined that the people of these countries would be offered Australian citizenship and relocation to Australian territory in exchange for Australian ownership of their territorial seas, exclusive economic zones, and fisheries.[22]
  • 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.[23][24]
  • In 2012, the Canadian and Danish governments were close to an agreement to declare Hans Island a condominium, after decades in dispute. On 11 June 2022, the Danish, Greenlandic, Canadian, and Nunavut governments compromised to divide Hans Island in half after 17 years of negotiations. On 14 June 2022, Canadian Foreign Affairs Minister Mélanie Joly, Danish foreign affairs minister Jeppe Kofod, and prime minister of Greenland Múte Bourup Egede signed a treaty to divide the island. By this, Canada and the Danish Realm, via Greenland, will have an international land border of 1,280 m (4,200 ft), which follows a rift, which forms a semi-circle with the westernmost part around the middle, in the surface of the island that runs from north to south near the centre of the island. On ratification, the island will contain the third shortest land border between countries, and will create a second land neighbour for Canada and the Danish Realm, each of which only had one, with the United States and Germany respectively. It will also create the northernmost international land border in the world, as well as the second land border between European and American countries, the previous one being between French Guiana (départment of France) and the South American countries Brazil and Suriname.[25]
  • Some proposed two-state solutions to the Israeli–Palestinian conflict involve a State of Israel and State of Palestine sharing sovereignty over part or all of Jerusalem.
  • In the talks between the UK and the People's Republic of China in 1983–84 over the transfer of sovereignty over Hong Kong, one of the British proposals was to transfer the sovereignty of Hong Kong and its dependencies to the People's Republic of China while the UK would retain the rights of administration of the territory.[26] The proposal was rejected and negotiations ended with the UK agreeing to relinquish all rights over Hong Kong to China in 1997.
  • In one proposed case of the Partition of Belgium, Brussels would become a condominium of Flanders and Wallonia.
  • In 1984, the New Ireland Forum suggested a proposal for joint UK/Irish authority in Northern Ireland to try to bring an end to the Troubles conflict. This idea was dismissed by the British government. The Good Friday Agreement of 1998 led to the establishment of a devolved power-sharing Northern Ireland Executive led jointly by the First and Deputy First Minister, positions nominated separately by the largest parties in each of the two largest community designations in the assembly. The proposal of joint authority by the UK and Irish governments over Northern Ireland was raised again in 2017 after the Irish backstop issue during the negotiations for the Brexit withdrawal agreement and the collapse of the power-sharing executive during the Renewable Heat Incentive scandal.[27]

See also


  2. Gómez Cruz, Ricardo Alonso (October 2004). Elementos Jurídicos para la Construcción de una Propuesta Tendente a la Recuperación Material y la Soberanía de la Isla Conejo en el Golfo de Fonseca (Legal Elements for the Construction of a Proposal to the Material Recovery and Sovereignty of Isla Conejo in the Gulf of Fonseca) (PDF) (Thesis). Universidad de El Salvador, Ciudad Universitaria, San Salvador, El Salvador. p. 33, 36, 46, 49 and 50. Retrieved 4 July 2013.
  3. Case Concerning Land, Island, and Maritime Frontier Dispute (El Salvador/Honduras, Nicaragua Intervening) (International Court of Justice 1992).Text
  4. Huezo Urquilla, Luis Salvador (July 1993). La controversia fronteriza terrestre, insular y maritima entre El Salvador y Honduras, y Nicaragua como país interviniente (Thesis). Universidad Dr. José Matías Delgado, San Salvador, El Salvador. Archived from the original on 15 March 2016. Retrieved 14 July 2013.
  5. Daniel-Erasmus Kahn (2004). Die deutschen Staatsgrenzen: rechtshistorische Grundlagen und offene Rechtsfragen ("The German national borders: legal-historical foundations and open legal questions"). Oxford University Press. ISBN 9783161484032.
  6. Smith, Barry. "Fiat Objects" (PDF). Department of Philosophy, Center for Cognitive Science and NCGIA, SUNY at Buffalo (NY). pp. 24–25. Retrieved 2 June 2013.
  7. Jacobs, Frank (12 January 2012). "The World's Most Exclusive Condominium". Retrieved 18 December 2016.
  8. "Select DEFRLUBEDELU.PDF (Map of condominium boundaries)". Retrieved 2 June 2013.
  9. The island that switches countries every six months, BBC News, 28 January 2018. Retrieved 2018-01-28.
  10. Coprince d'Andorre, Hollande rend visite à la principauté, Le Parisien, 12 June 2014
  11. Zavagno, L. (2013). Two hegemonies, one island: Cyprus as a "Middle Ground" between the Byzantines and the Arabs (650–850 A.D.). Reti Medievali Rivista.,%20one%20island.pdf.
  12. Jozo Tomasevich. "The Chetniks". War and Revolution in Yugoslavia. Stanford University Press, 1975. Pp. 103. "The condominium in Croatia was the most important example of Italo-German collaboration in controlling and despoiling an occupied area [...]".
  13. Stephen R. Graubard, (ed.).Exit from Communism. Transaction Publishers, 1993. Pp. 153–154. "After the Axis attack on Yugoslavia in 1941, Mussolini and Hitler installed the Ustašas in power in Zagreb, making them the nucleus of a dependent regime of the newly created Independent State of Croatia, an Italo-German condominium predicated on the abolition of Yugoslavia."
  14. Günay Göksu Özdoğan, Kemâli Saybaşılı. Balkans: a mirror of the new international order. Marmara Üniversitesi. Dept. of International Relations, 1995. Pp. 143. "Croatia (with Bosnia-Hercegovina) formally became a new Axis ally – the Independent State of Croatia (NDH). This was in fact, Italo-German condominium, [...]".
  15. John R. Lampe (ed.), Mark Mazower (ed.). Ideologies and National Identities: The Case of Twentieth-Century Southeastern Europe. Central European University Press, 2003. Pp. 103. "[...] the Independent State of Croatia (hereafter NDH, Nezavisna Drzava Hrvatska), in reality an Italo-German condominium[...]"
  16. "Archived copy" (PDF). Archived from the original (PDF) on 4 October 2011. Retrieved 29 August 2011.{{cite web}}: CS1 maint: archived copy as title (link)
  17. The UAE: Internal Boundaries and the Boundary with Oman. Vol. 6. pp. 477–478. ISBN 1-85207-575-9.
  18. "Ajman/Muscat condominium". Archived from the original on 30 December 2019. Retrieved 14 January 2017. I don't know when the Hadf zone agreement was terminated, but it certainly was.
  19. "Bulgaria".
  20. Bromley, J S (editor) 1970, The New Cambridge Modern History Volume 6: The Rise of Great Britain and Russia, 1688-1715/25, Cambridge University Press, ISBN 978-0521075244 (p. 428)
  21. Namibia Yearbook, Issue 3, pages 18
  22. The Complacent Country Archived 10 June 2020 at the Wayback Machine Kevin Rudd. 4 February 2019
  23. CIA – The World Factbook – Gibraltar US Central Intelligence Agency
  24. BBC News | Europe | Country profiles | Regions and territories: Gibraltar BBC News
  25. The treaty has yet to be ratified by the Parliament of Canada, the Folketing (Parliament of Denmark), the Inatsisartut (Parliament of Greenland) and the Legislative Assembly of Nunavut. The treaty will go into effect after aforementioned governments ratify the treaty.
  26. How Mrs Thatcher lost Hong Kong, The Independent, Robert Cottrell, 30 August 1992
  27. SDLP backs British-Irish rule if Northern Ireland devolution fails, The Guardian, 11 January 2017
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