## Facts

- Spain’s colonial administration in Central America later became the Federal Republic of Central America; after its collapse in the early 19th century, El Salvador and Honduras emerged with uncertain internal administrative lines that later hardened into contested international frontiers.
- Boundary disagreements between El Salvador and Honduras persisted for decades and contributed to armed conflict in 1969.
- The States concluded the General Treaty of Peace in 1980, creating a Joint Frontier Commission to settle parts of the land boundary and providing for submission of remaining disputes to the International Court of Justice.
- By Special Agreement signed in 1986, El Salvador and Honduras asked the ICJ to decide their outstanding “land, island and maritime frontier dispute,” including (1) six segments of the land frontier, (2) sovereignty over islands in the Gulf of Fonseca, and (3) the legal status of the Gulf’s waters and related maritime areas.
- The ICJ constituted a Chamber under Article 26(2) of the Statute to hear the case.
- Nicaragua, which also borders the Gulf of Fonseca, sought permission to intervene under Article 62, claiming that the Court’s decision on the Gulf’s waters could affect its legal rights.
- In a 1990 judgment on intervention, the Chamber allowed Nicaragua to intervene only as to the legal régime of the Gulf of Fonseca’s waters; Nicaragua did not become a party and the Chamber did not accept Nicaragua as a participant on the land boundary, island sovereignty, or any Nicaragua–El Salvador/Honduras delimitation.
- The merits phase proceeded through extensive written pleadings and lengthy hearings addressing colonial title, post-independence conduct, and the law of the sea consequences of the Gulf’s status and any boundary outside the Gulf.
- The dispute required the Chamber to apply Spanish-American boundary doctrine (including *uti possidetis juris*), evaluate acts showing actual exercise of authority, and frame any maritime line so it would not decide Nicaragua’s separate maritime boundaries.

## Issues

1. What is the correct delimitation of the six disputed land-frontier sectors between El Salvador and Honduras based on the applicable titles at independence and later conduct?
2. Which State has sovereignty over principal islands in the Gulf of Fonseca, including Meanguera, Meanguerita, and El Tigre?
3. What is the juridical status of the Gulf of Fonseca and what rights do El Salvador, Honduras, and Nicaragua have in its waters?
4. To what extent may the Chamber draw any maritime boundary lines (inside the Gulf framework and in the Pacific outside the Gulf) while keeping Nicaragua’s rights as a non-party protected?

## Decision

- The Chamber delimited all six disputed land sectors, treating *uti possidetis juris* at independence as the main basis for title and using effectivités to confirm or resolve uncertainties where documentary title was unclear.
- The Chamber awarded sovereignty over Meanguera and Meanguerita to El Salvador and sovereignty over El Tigre to Honduras, relying on historical title materials and, where needed, evidence of actual administration.
- The Chamber held that the Gulf of Fonseca has the character of historic waters (a historic bay) and that El Salvador, Honduras, and Nicaragua hold a shared legal régime in the Gulf’s waters, with joint rights that prevent any one of them from treating the Gulf as solely its own.
- Consistently with that legal régime and the Special Agreement, the Chamber identified lines relevant to the Parties’ maritime relations while stating that nothing in its decision would determine maritime boundaries between Nicaragua and either principal party.
- For maritime space in the Pacific Ocean outside the Gulf, the Chamber drew a bilateral El Salvador–Honduras maritime boundary using an equidistance method as a starting point and adjusting it in light of the coastal geography, while expressly limiting the ruling to the two parties before it.

## Legal Principles

- *Uti possidetis juris* in Spanish-American successor-State disputes converts colonial administrative limits at independence into international boundaries; the task is to ascertain the legal title as it stood at independence from the best available historical materials.
- Effectivités (actual, peaceful display of State authority) can help interpret, confirm, or fill gaps where title is uncertain, but they do not defeat a clear legal title derived from *uti possidetis juris*.
- Historic waters/historic bay status may arise from long-standing history and recognition; where multiple successor States inherit such a status, the result may be a shared legal régime in which rights are joint rather than exclusive.
- Article 62 intervention requires an “interest of a legal nature which may be affected” by the decision; intervention does not make the intervening State a party and does not permit the Court to decide a new dispute between the intervenor and the principal parties.
- When a third coastal State is present, the Court may state principles and draw bilateral lines only to the extent necessary to decide the case submitted, and must frame the dispositif so it does not decide the third State’s maritime boundaries.

## Conclusion

The ICJ Chamber settled major components of the El Salvador–Honduras frontier dispute left open after the 1980 peace treaty by fixing six land-boundary sectors, deciding sovereignty over leading Gulf of Fonseca islands, and declaring the Gulf to be historic waters subject to a shared three-State legal régime, while also drawing a limited bilateral maritime boundary outside the Gulf and protecting Nicaragua’s legal interests through a narrow Article 62 intervention.


Land, Island and Maritime Frontier Dispute—El Salvador/Honduras; Nicaragua Intervening, 1992 ICJ Rep. 350 (Judgment of September 11) (1992)