Summary: On June 6, 2016, Chile instituted proceedings against Bolivia with regard to a dispute concerning the status and use of the waters of the Silala, a water feature along the border of both countries. Chile asserts the Silala qualifies as an international river under the UN Watercourses Convention and a long practice by both States of referring to the watercourse as the Silala River. Chile also claims that its use of the waters was authorized under the 1904 Treaty of Peace and Friendship and subsequent 1908 Concession. Bolivia is expected to respond to this application..

Summary: In 2011, Costa Rica constructed a Route 1856 parallel to the San Juan River from Los Chiles to the Delta region. Nicaragua contended that the road caused harmful environmental effects to Nicaraguan territory through silting of the San Juan River, erosion of the River's banks, and harm to the surrounding environment and wetlands. Nicaragua further contended that Costa Rica breached its international obligations by infringing on Nicaragua's territorial integrity, damaging Nicaraguan territory, and violating general obligations in international law and relevant environmental conventions. On 17 April 2013, the Court joined the case with that of Certain Activities carried out by Nicaragua in the Border Area (Costa Rica v. Nicaragua).

On 16 December 2015, the Court issued its decision in both cases. In the dispute related to Isla Portillos, the Court concluded that Costa Rica held sovereignty over the territory and Nicaragua's actions constituted an unlawful incursion. In the disputed related to Costa Rica's road, the Court ruled that Costa Rica violated its obligations to Nicaragua to conduct an environmental impact assessment prior to constructing the road, a project that could have caused significant transboundary harm. The Court, however, concluded that Nicaragua failed to establish that the ensuring harm rose to the level of significant.

The ICJ gave Costa Rica and Nicaragua twelve months to agree on the amount of compensation Costa Rica should receive from Nicaragua for Nicaragua's territorial incursion. If the Parties are unable to reach an agreement, either Party may then request the ICJ determine the proper amount of compensation.

Summary: Costa Rica contended that from August through November 2010, Nicaragua felled trees and dredged the San Juan River to build a canal across Isla Portillos. In so doing, Costa Rica contends that Nicaragua's Army incurred onto and occupied Costa Rican territory in violation of Costa Rica's rights and obligations Nicaragua owed Costa Rica under several international treaties and conventions.

Nicaragua responded that the activities they undertook where on Nicaraguan territory. In 2011, the ICJ ordered provisional measures: mandating that neither party maintain personnel in the disputed territory; permitting Costa Rica to send civilian personnel to the disputed territory to protect the environment from potential irreparable harm; prohibiting both parties from engaging in activity that may further aggravate the dispute before the Court renders its final decision; and requiring both parties to inform the Court of its compliance.

On 17 April 2013, the Court joined the case with that of Construction of a Road in Costa Rica along the San Juan River (Nicaragua v. Costa Rica On 16 December 2015, the Court issued its decision in both cases (see above).

Summary: In 2003, Uruguay authorized the construction of pulp mills on the Uruguay River. In 2006, Argentina initiated proceedings to prevent Uruguay from constructing the mills. Argentina claimed that Uruguay violated treaty provisions that require prior notification and consultation before taking actions that could affect river water quality.

The Court rejected Argentina's request for a preliminary injunction, stating that Uruguay intended to and could still comply with its international obligations. As a result, protesters in Argentina blockades roads to prevent construction. When Argentina appealed to the Court a second time, Uruguay also sought relief from Argentina's protests. The Court rejected both requests because neither state presented risks of prejudice to their rights under the treaty.

On 20 April 2010, the Court concluded that while Uruguay breached its international procedural obligations to notify and consult with Argentina before authorizing and commencing construction on the pulp mills, the Court's declaration of Uruguay's breach constituted a sufficient remedy for Argentina's claim.

Summary: In 2005 Costa Rica initiated proceedings against Nicaragua for allegedly breaching treaty obligations and other international responsibilities by restricting Costa Rica's navigational rights on the San Juan River.

The Court held that Nicaragua has the right to regulate activity on the river for national security reasons. Accordingly, much of Nicaragua's regulatory scheme did not unlawfully violate Costa Rica's right of free navigation "for the purposes of commerce." The Court did find, however, that Nicaragua went too far in requiring visas and tourist cards and by imposing fees on Costa Rican vessels.

Summary: The Republic of Benin and the Republic of Niger asked the International Court of Justice to determine the international boundary along the River Niger and River Mekrou sectors, which separate the two republics. Benin and Niger also disputed the ownership of several islands within the River Niger sector and asked the Court to specify which State owns each of the islands.

The Court applied the principle of Uti Possidetis Juris, which allows administrative delimitations established during a colonial periods to become international frontiers at the moment when independence is achieved. Because Benin and Niger both escaped the colonial control of France in the 1960s, the Court identified the administrative boundaries that existed during France's colonial administration and endorsed them as the official boundary between the States.

Summary: The Kasikili/Sedudu Island lies in the Chobe River on the border between Botswana and Namibia. Botswana and Namibia asked the International Court of Justice to determine the international boundary and legal status of the Island based on the Anglo-German Treaty of 1 July 1890 and general principles of international law. The parties agreed that the Anglo-German Treaty, which defines the boundary along the Chobe River, was binding on them as successor states to Great Britain and Germany.

In applying the terms of the Treaty, the Court found that the Island is within the borders of Botswana. Additionally, the Court rejected Namibia's alternative claim of prescription because Namibia's predecessor used the Island without claiming territorial sovereignty, and when Namibia did claim title, Botswana's predecessor rejected that claim and thus precluded Namibia's subsequent claim of prescriptive title.

Summary: In 1977 Hungary and Czechoslovakia signed a treaty obligating the States to cooperate in the construction of a system of dams and locks along a section of the Danube River that formed the border between the States. Construction commenced in 1978 but progressed slowly due to political and economic transformations in both States. In 1989, Hungary abandoned the project, justifying its decision on claims of changed circumstances and impossibility.

In 1993, Czechoslovakia peacefully separated into two nations: Czech Republic and Slovakia. Slovakia assumed its predecessor's responsibilities under the treaty because the planned hydraulic system fell within its territory along the Danube River. After continued negotiations failed, Slovakia devised "Variant C," an alternative plan to complete the project. Under Variant C, Slovakia dammed the Danube and appropriated between 80 and 90% of the river water.

The dispute came before the International Court of Justice in 1994 and was decided in 1997. The Court rejected Hungary's claims of changed circumstances and impossibility but also concluded that Slovakia, by putting Variant C into operation and unilaterally taking control of a shared resource, had violated international law and the 1977 Treaty. Ultimately, the Court ordered the parties to "re-establish co-operative administration of what remains of the Project."

Summary: In 1839, the Federal Republic of Central America broke up, and Honduras, El Salvador, Costa Rica, Guatemala, and Nicaragua became independent states. By 1986, Honduras and El Salvador were still in disagreement over six sectors of the boundary between them. Thus Honduras and El Salvador submitted a Special Agreement to the International Court of Justice to resolve their boundary dispute. They also asked the Court to rule on the legal status of islands and other maritime areas within the Gulf of Fonseca.

Regarding certain maritime aspects of the case, the Court allowed Nicaragua to intervene. The Court and the parties agreed that the principle of Uti Possidetis Juris should operate to create international frontiers where administrative boundaries existed prior to independence of the countries. Accordingly, based on documentary evidence of administrative boundaries, the Court delimited the boundary in the disputed areas. For some areas where evidence was insufficient, the Court gave weight to watersheds and other identifiable topographical features.