Years in the making, Sovereign Limits is a database of international boundaries intended for use in the research, visualization, and mapping of the borders that divide up sovereignty on land and sea.

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International Court Settles Land, Maritime Disputes between Costa Rica and Nicaragua

February 16, 2018
Meghan Gilbert

The International Court of Justice (ICJ) delivered a Judgment on 2 February 2018 that resolved the land and maritime disputes between Costa Rica and Nicaragua. The Court delimited the maritime boundary, reaffirmed Costa Rican sovereignty over Isla Portillos, and ordered the Nicaraguan government to remove a military camp located in the wetland of Isla Portillos.

This is not the first time that arbitration has occurred to resolve disputes between the two countries. Their boundary was arbitrated by the United States during the 19th century, and in 2010, Costa Rica initiated proceedings against Nicaragua at the ICJ following the establishment of a Nicaraguan military camp in Isla Portillos. The Court ruled in 2015 that the presence of the camp violated Costa Rican sovereignty.

Nicaragua withdrew its troops from Isla Portillos in accordance with the 2015 Judgment but constructed a new camp within the area in the following months. Costa Rica filed new proceedings in January 2017 and argued that the Court had already ruled that Costa Rica held sovereignty over the area.

In 2014, Costa Rica initiated a case against Nicaragua concerning the maritime boundary following unsuccessful bilateral talks and the Nicaraguan allocation of disputed maritime space to several oil companies. The Court decided to join the proceedings of the Isla Portillos and maritime disputes, which led to this Judgment.

The Isla Portillos dispute stems from conflicting interpretations of a 19th century border treaty and arbitration. The features described in the treaty have disappeared due to coastal recession, which prompted the Court to redefine the boundary in the absence of these historic features. They ultimately allocated Isla Portillos to Costa Rica and Harbor Head Lagoon to Nicaragua.

Map depicting the boundary along Isla Portillos. Source: ICJ Judgment.

The Court delimited a single boundary along the territorial sea, exclusive economic zone (EEZ), and continental shelf using the principle of equidistance.

For the Caribbean maritime boundary, strict equidistance was modified by the Court to give the Corn Islands (Nicaragua) half-effect. The Court also addressed several other issues concerning this boundary, including a frequently changing coastline and the overlapping entitlements of third States.

The Caribbean maritime boundary delimited by the Court. Source: ICJ Judgment.

Erosion along the mouth of the San Juan River frequently alters the shape of the Caribbean coastline. Taking this into account, the Court established a fluid starting point of the maritime boundary that lies wherever the mouth of the San Juan River is currently located, and a fixed point two nautical miles out to sea.

This approach is similar to the Court’s treatment of other cases involving volatile coastlines. In Honduras v. Nicaragua, the Court established the starting-point of the maritime boundary at a distance of three nautical miles seaward from the mouth of the Coco River due to the instability of the coastline in that area.

The Court treaded cautiously regarding overlapping entitlements of third States in the Caribbean. Colombia and Panama have both delimited boundaries in the relevant maritime area in this case. The Judgment emphasizes that the establishment of the maritime boundary is without prejudice to any overlapping claims or entitlements of third States, as the maritime space of third States cannot be identified in the proceedings of the case.

The Judgment’s effect on third States remains to be seen, however it will likely have significant impact on future maritime boundary negotiations in the Caribbean, especially if Colombia and Panama stake additional claims in the area.

The Pacific maritime boundary is more straightforward than that of the Caribbean. Half-effect was given to the Santa Elena Peninsula (Costa Rica) to obtain a more equitable division of the relevant maritime space.

Map of the Pacific maritime boundary. Source: ICJ Judgment.

Both States have hailed the proceedings as a victory in government press releases. The Judgment will likely have a significant effect on Costa Rican–Nicaraguan relations and maritime boundary negotiations in the Caribbean Sea involving other States.

The full text of the Judgment can be accessed here.

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