Beagle Channel arbitration
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: 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: 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: The controversial articles II and III of the 1881 treaty were: Under  the so-called oceanic principle Argentina believed that the "uti possidetis" doctrine operated such that, under the arrangements operated by the colonial administrations, Chile (then the Captaincy General of Chile) had no territorial waters in the Atlantic Ocean and the Argentine (then the Viceroyalty of the Río de la Plata) could not have territorial waters in the Pacific Ocean. The Argentine saw a reaffirmation of this principle in the Protocols of 1902, according to Rizzo Romano the first arms control pact in the world, under which both countries agreed that the Chilean navy should have enough ships to defend the  interests of Chile in the Pacific, and the Argentine navy should have enough ships to defend the interests of Argentina in the Atlantic. Chile doesn't consider the 1902 protocol as a border treaty and the word "Pacific" doesn't appear in the Boundary treaty, and hence claimed that the boundary between the Pacific and the Atlantic had never been defined. To resolve the conflicting interests of both countries, they decided in 1881 on an agreement; but nearly a century later there was still no mutual understanding of what that agreement had consisted of. Chile maintained it had only renounced  rights to eastern Patagonia (today continental south Argentina) to obtain full possession of the Strait of Magellan, but Argentina believed Chile received the Strait of Magellan in return for renouncing all coasts bordering the Atlantic Ocean. About the course of the Beagle Channel there were discrepancies. The eastern end of the Channel can be seen as a delta with an east-west arm and a north-south arm (around Navarino Island). The channel specified in the border treaty of 1881 was seen by Chile as the east-west arm, but by Argentina as the north-south arm. Following this controversy , two clauses were in dispute: Chile argued the Channel clause ("... to Chile shall belong all the islands to the south of Beagle Channel up to Cape Horn..."), while Argentina the Atlantic clause ("... the other islands there may be on the Atlantic to the east of Tierra del Fuego ..."). Some Chileans argued that the text ""until it touches the Beagle Channel"" in article III meant that Argentina had no navigable waters in the Beagle Channel, although this interpretation was not supported by the Chilean claim. The judgement. A unanimous judgement was handed over to Queen Elizabeth II on 18 April 1977 . The French judge André Gros gave a dissenting vote, not concerning the result but the reason. On 2 May 1977 the judgement was announced to the governments of both countries. It involved the border running approximately along the center of the Channel, and awarded both Chile and Argentina sovereignty over navigable waters in the Channel: Whaits island, the islets called Snipe, Eugenia, Solitario, Hermanos, Gardiner and Reparo, and the bank known as Herradura were awarded to Chile. All of these lie near the southern bank of the Beagle Channel. Argentina was awarded all islands, islets and rocks near the north  coast of the channel: Bridges, Eclaireurs, Gable, Becasses, Martillo and Yunque. At the eastern end of the Channel, the judgement recognized the sovereignty of Chile over the Picton, Nueva and Lennox islands and all their adjacent islets and rocks. The territorial waters established by these coasts, according to international maritime law, established Chilean rights in the Atlantic Ocean. The Court sentenced also: The reasons of the Court. The court rejected both the uti possidetis principle and the oceanic principle because: The tribunal considered that the exchange of Patagonia for the Strait of Magellan was the transaction behind the 1881 treaty : After careful consideration of all possible word meanings and interpretations of the text, the court refused the Atlantic clause: The reaction to the judgement. Chile accepted the judgement immediately and enacted it into its domestic law on 14 June 1977 (decree n°416 over the base lines). On 25 January 1978 Argentina repudiated the arbitration award. According to Argentina: It has been argued that the Argentine claims over the Beagle Channel could not be sustained from a legal point of view and that in practice many of their assertions were subjective. Aftermath. The court awarded navigable waters on the  north bank of the eastern part of the Channel to Argentina, but otherwise it met all Chilean claims. Although the arbitration concerned only small islands, the direction of the new demarcation of the frontier would under international maritime law give Chile significant rights running into the Atlantic Ocean, and would also significantly reduce the claims of Argentina on the Antarctic continent and its waters. The Argentine rejection led both countries to the verge of war. On 22 December 1978 Argentina started military action to invade the islands. Only last minute papal mediation prevented the outbreak of armed conflict. The award  was a defeat for Argentine foreign policy and initiated an uncoupling from the international community. The arbitration was completely separate from the Falkland Islands issue, a fact that is often obfuscated or publicly denied in Argentina, where the arbitration is often presented as a plot by the UK. Pablo Lacoste in his work ""La disputa por el Beagle y el papel de los actores no estatales argentinos"" (Argentine Civil Society Agencies in the Beagle Dispute) says: Chile kept in mind the Argentine breach of the arbitration agreement. The award brought the military dictatorships on both sides to the border to  a unique and paradoxical situation: in Chile they celebrated the "wise" decision of the (overthrown) enemy Allende, and in Argentina they criticized the "imprudent" decision of his former colleague in power, general Lanusse. The award was later fully recognized by Argentina in the Peace and Friendship Treaty of 1984.