## Facts

- Burkina Faso (formerly Upper Volta) and Mali, both former French West Africa territories, disagreed over the course of their land frontier in a disputed band of territory from the Koro (Mali)–Djibo (Burkina Faso) sector to the Béli region.
- The states submitted the dispute by Special Agreement (Sept. 16, 1983) to a Chamber constituted under Article 26(2) of the ICJ Statute, requesting determination of the frontier line in the defined disputed area.
- A five-judge Chamber was constituted by order of Apr. 3, 1985; the judgment would have the same force as a judgment of the full Court.
- During proceedings, armed incidents occurred in late 1985; on Jan. 10, 1986, the Chamber indicated provisional measures requiring, among other things, withdrawal of forces from the disputed area to an agreed line or a line set by the Chamber.
- The parties presented colonial-era legal instruments, administrative records, maps, and evidence of colonial administrative practice (“effectivités”) bearing on the location of the colonial boundary at independence (1959–60).
- On Dec. 22, 1986, the Chamber unanimously fixed the course of the frontier throughout the disputed sector, including its endpoint at the vicinity of the tripoint with Niger.

## Issues

1. What was the line of the Burkina Faso–Mali frontier in the disputed area as it existed at independence, derived from the former colonial administrative boundary?
2. How should the Chamber weigh colonial legal texts, administrative practice (effectivités), and cartographic materials when they point in different directions?
3. Whether, and to what extent, equitable considerations could be used in delimiting the frontier without departing from applicable law.
4. Whether the Chamber could determine a frontier segment terminating at a tripoint on Niger’s boundary without Niger’s participation.

## Decision

- The Chamber applied the principles of intangibility of inherited colonial frontiers and *uti possidetis juris* to transform the relevant colonial administrative boundary into the international frontier at independence.
- The Chamber determined a continuous frontier line for the entire disputed area, specifying it by reference to identified localities, natural features, and coordinates.
- The Chamber treated effectivités as supplementary or confirmatory, and held that where legal title was clear, it prevailed over inconsistent administrative practice.
- The Chamber used equity only *infra legem*—as an interpretive method within the law—to resolve ambiguities, not to redraw an established boundary.
- The Chamber held it could define the boundary up to the tripoint with Niger; Niger’s rights were not decided because the judgment was binding only between Burkina Faso and Mali under Article 59 of the ICJ Statute.

## Legal Principles

- *Uti possidetis juris* in decolonization converts pre-independence administrative boundaries into international frontiers to preserve stability at independence.
- In boundary disputes governed by *uti possidetis juris*, legal title found in authoritative instruments has priority over effectivités when they conflict.
- Effectivités may assist in interpretation where the legal title is unclear, incomplete, or ambiguous, but cannot override a clear legal delimitation.
- Equity *infra legem* may guide interpretation and application of existing law to resolve uncertainty, but does not authorize decision *ex aequo et bono* or departure from established legal boundaries.
- An adjudicatory body may determine a frontier up to a tripoint adjoining a third state, while safeguarding the third state’s rights by limiting the judgment’s binding effect to the parties.

## Conclusion

The Chamber resolved the Burkina Faso–Mali frontier dispute by giving controlling weight to colonial legal title under *uti possidetis juris*, using effectivités only as support where needed and equity only as a lawful interpretive aid, and it confirmed that delimitation up to a tripoint does not bind an absent third state.


Frontier Dispute (Burk. Faso v. Mali), 1986 I.C.J. 554 (Dec. 22)