On 27 January 2014, the International Court of Justice (the ICJ or the Court) delivered its judgment in the Maritime Dispute (Peru v Chile) case, which concerned the delimitation of the maritime boundary between Peru and Chile in the Pacific Ocean. The judgment brings to an end a six-year legal proceeding.

The judgment is particularly noteworthy in view of its conclusion that the parties had previously agreed a single maritime boundary, extending 80 nautical miles due west from the end of the land border. The Court then proceeded to draw the rest of the maritime boundary based on the principle of equidistance in accordance with the Court’s standard three-step methodology. Both Peru and Chile have hailed the judgment as a partial victory and have pledged to abide by it.


On 16 January 2008, Peru instituted proceedings against Chile in the ICJ. The key issue in dispute was whether the two countries had previously agreed upon a maritime boundary. It was Peru’s submission that there was no agreed maritime boundary, and therefore that the ICJ should delimit the maritime zones between Peru and Chile using a line equidistant from the baselines of both parties. Conversely, Chile submitted that the parties had already delimited their maritime boundary by agreement, under the Santiago Declaration of 1952 (the 1952 Declaration). Under the 1952 Declaration, Chile claimed, the boundary should extend for 200 nautical miles due west from the point where the land border meets the sea. 

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Judgment of the ICJ

The ICJ began its analysis by conducting an extensive review of the relevant agreements and practices of the parties in order to determine whether an agreed maritime boundary was already in existence. In particular, it held that neither the unilateral proclamations issued by both Peru and Chile in 1947, nor the 1952 Declaration, established a maritime boundary. However, it found that the terms of the 1954 Special Maritime Frontier Zone Agreement (the 1954 Agreement) acknowledged that a maritime boundary already existed, although this did not indicate the nature of the boundary (or when it was agreed).

In order to delineate the precise parameters of this previously agreed boundary, the ICJ had regard to 1950s fishing practices (as the 1954 Agreement concerned the regulation of fishing activity) as well as the law of the sea in the early 1950s. In particular, the Court noted that claims to a maritime zone extending to a minimum distance of 200 nautical miles were not in accordance with international law at that time. As a result, the ICJ concluded (by fifteen votes to one) that there was an agreed maritime boundary running due west from the coastal border shared by the two States, and (by ten votes to six) that it extended for 80 nautical miles (Point A).

The ICJ then ruled on the delimitation of the boundary beyond this point, applying the three-step procedure set down in previous case law (for example the Romania v Ukraine andNicaragua v Colombia judgments of 2009 and 2012 respectively):

First step: Construction of equidistance line

The ICJ constructed a provisional equidistance line which was extended out to 200 nautical miles from the Chilean coast. This boundary was drawn running south-west from Point A (toPoint B), with an additional 22 nautical miles due south (to Point C) to the point where the 200 nautical mile limits of the parties’ maritime entitlements intersect.

Second step: Consideration of special circumstances on grounds of equity

The ICJ found that there were no relevant circumstances which called for an adjustment of the provisional equidistance line on grounds of equity.

Third step: Proportionality

The ICJ then examined whether the provisional equidistance line produced a result which was significantly disproportionate in terms of the lengths of the relevant coasts and division of the relevant area, and concluded that no significant disproportion was evident in this case.

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The focus of the judgment is on the first question of whether the parties had reached agreement in relation to delimitation of the maritime boundary. The fact that such an agreement had not been specifically documented led the Court to undertake a very broad-ranging empirical exercise, considering not just treaties, but diplomatic correspondence, domestic legislative practice, fishing and enforcement activity and statements made at the Third UN Conference on the Law of the Sea.

The outcome is most notable, therefore, for the conclusion reached on the basis of this evidence (which was upheld by only a 10 to six majority). The Court’s subsequent analysis of the provisional equidistance line was brief and relatively uncontroversial (Chile did not in fact make submissions on the point).

The result represents something of a compromise between the claims of the two parties, with Peru having been awarded more than half of the disputed 38,000 square kilometre area of ocean, and Chile having retained the bulk of the valuable coastal fishing grounds in the area. Both countries have pledged to abide by the judgment, which should, in the long term, do much to improve ties between the two fast-growing economies, whose bilateral trade totalled $3 billion in 2013.

Finally, it bears noting that this area of coastline will be considered again by the ICJ in the context of the proceedings instituted by Bolivia against Chile in April 2013, seeking the granting of “sovereign access” to the Pacific Ocean.