On 22 July 1971 Salvador Allende and Alejandro Lanusse, the Presidents of Chile and Argentina, signed an arbitration agreement (the Arbitration Agreement of 1971). This agreement related to their dispute over the territorial and maritime boundaries between them, and in particular the title to the Picton, Nueva and Lennox islands near the extreme end of the American continent, which was submitted to binding arbitration under the auspices of the United Kingdom government.
On 2 May 1977 the court ruled that the islands belonged to Chile (see the Report and decision of the Court of Arbitration). On 25 January 1978 Argentina repudiated the arbitration decision and on 22 December 1978 started (and a few hours later aborted) military action to invade both those islands and continental Chile.
The Court
The British Crown had previously in 1902 and 1966 acted as arbitrator between Chile and Argentina (see Arbitration 1902 here), but on this occasion the statutory framework of the Arbitration was different.
The Arbitration Agreement of 1971 stipulated: the names of the five judges appointed (see the preamble of the Arbitration Agreement): Hardy Cross Dillard (United States of America) Gerald Fitzmaurice (United Kingdom) André Gros (France) Charles D. Onyeama (Nigeria) Sture Petrén (Sweden) the region where the court was to define the borderline (A polygon ABCDEF, known as "Hammer", see paragraph 4 of Article 1 of the Arbitration Agreement) that the final decision would be submitted to the British Crown, which was then to recommend acceptance or rejection of the award of the court but not to modify it (Article XIII of the Arbitration Agreement) that the Court of Arbitration should reach its conclusions in accordance with the principles of international law. that each of the Parties should defray its own expenses and one half of the expenses of the Court of Arbitration and of Her Britannic Majesty's Government in relation to the Arbitration.
In this way the United Kingdom did not have any influence on the judgement: the procedure, the legal framework, the judges and the matter in dispute had all been defined by both countries.
Procedure
The procedure had four phases:
The Memorials (starting from 1 January 1973) in terms of the delivery of written pleadings, annexes and maps. The Counter-Memorials (starting from 2 June 1974) in terms of the responses. The Replies (starting from 1 June 1975) in terms of comments. The Oral proceedings (starting from 7 November 1975 to 23. October 1976) in terms of oral statements that were made in English or French at the speaker's choice, a simultaneous translation into English being provided in the latter case.
Chile handed over to the Court 14 volumes and 213 maps, and Argentina 12 volumes and 195 maps.
During the first fortnight of March 1976, the Court, accompanied by the Registrar and Liaison Officers from both sides, visited the Beagle Channel region, and inspected the islands and waterways concerned, first on the Chilean Naval Transport Vessel "Aquiles", and then on the Argentine Naval Transport Vessel "ARA Bahia Aguirre".
Arguments
In the border treaty of 1855 Chile and Argentina had agreed to retain the borders of the Spanish colonial administration. This principle, known in jurisprudence as Uti possidetis, served two purposes: the first was to divide the territory between the two countries, and the second to preclude the creation of Res nullius areas that could have been taken in possession by other powers (such as the United States of America, the UK or France – although the Beagle Channel had been unknown until 1830 and there had been no Spanish settlements south of Chiloé).
The boundary treaty of 1881 described, without any map, the course of the 5600 km border as follows: over the Andes mountains (from north to parallel 52°S: 'the highest peaks that divide the waters') (Article I), in the region north of and through the Strait of Magellan (mainly along the 52°S parallel) (Article II) and in the Tierra del Fuego-Beagle Channel region (Article III).
The controversial articles II and III of the 1881 treaty were: