Land and Maritime Delimitation and Sovereignty over Islands (Gabon/Equatorial Guinea)

Article by Kanyiri Kariuki, Advocate of the High Court of Kenya.

I.CASE INFORMATION 

On 19 May 2025, the International Court of Justice (ICJ) delivered its judgment in the case concerning Land and Maritime Delimitation and Sovereignty over Islands between the Gabonese Republic and the Republic of Equatorial Guinea, based on a Special Agreement notified to the Court in 2021. The Court was tasked with identifying which legal titles, treaties, and international conventions invoked by the Parties had the force of law concerning: (1) the delimitation of their common land boundary; (2) the delimitation of their common maritime boundary; and (3) sovereignty over the islands of Mbanié/Mbañe, Cocotiers/Cocoteros, and Conga.  

II. PARTIES' CLAIMS AND ARGUMENTS 

Equatorial Guinea's core position was that the Court should determine which legal titles, treaties, and international conventions had the force of law in their relations concerning the dispute. Gabon's main contention was that the 1974 "Bata Convention" was a legally binding treaty that settled the disputes. 

The parties addressed themselves on the issues as follows: 

Interpretation of "Legal Titles":  

Equatorial Guinea argued that the term "legal titles" in the Special Agreement is broad and not limited to treaties and international conventions. It contended that "legal titles" encompasses any source of rights to territory under international law, including State succession, the principle that "the land dominates the sea," and the principle of uti possidetis juris. Initially, Gabon maintained that "legal titles" should refer solely to "treaties and international conventions". While seemingly conceding later that "legal titles" could embrace more than documentary evidence, it consistently argued that State succession, the "land dominates the sea" principle, and uti possidetis juris did not fall within that scope. It expressly denied that effectivités could constitute a legal title. 

Land Boundary Delimitation:  

Equatorial Guinea submitted that the legal titles having force of law for the land boundary are the succession by Equatorial Guinea to titles held by Spain and by Gabon to titles held by France, both based on the 1900 Convention. This included titles to territory held on the basis of modifications made in the application of the 1900 Convention to the boundary described in its Article IV. It argued that the provisions for modification in the 1900 Convention were applied and given effect in the Utamboni River and Kie River areas. It relied on effectivités to "confirm" the existence of a right derived from a legal title.  

Gabon invoked the "Bata Convention" and the 1900 Convention, subject to modifications made by the "Bata Convention," as the legal titles for the land boundary. It contended that any proposals for boundary modification under the 1900 Convention required explicit governmental approval, a condition it argued was not satisfied for the Utamboni River area. 

Regarding the Kie River area, Gabon argued that the 1919 Governors' Agreement was not concluded pursuant to the 1900 Convention's modification procedures. It considered the 2007 Border Bridges Agreement merely an "arrangement of convenience". 

Sovereignty over Mbanié/Mbañe, Cocotiers/Cocoteros, and Conga:  

Equatorial Guinea invoked its succession to the title held by Spain on 12 October 1968 over these islands as its legal title. It relied on Spain's "public and notorious assertion of sovereignty without protest" and alleged agreements with local people. It referred to a series of instruments indicating Spanish colonial claims. It argued that the 1900 Convention confirmed France's recognition of Spain's pre-existing title to Corisco Island, and by extension, to the disputed islands as dependencies. It cited the 1955 beacon incident on Cocotiers/Cocoteros as an example of Spanish authority. It presented evidence of post-independence effectivités.   

Gabon invoked the "Bata Convention" as the sole legal title having the force of law for sovereignty over these islands. It argued that the 1778 Treaty of El Pardo was irrelevant as it did not mention the disputed islands. It contended that other historical documents invoked by Equatorial Guinea were unilateral acts of Spain. Gabon asserted that Equatorial Guinea could not invoke both occupation and agreements with local rulers as mutually exclusive theories.It maintained that France and Gabon had long made competing claims to the islands.It emphasized that the 1900 Convention was silent on the disputed islands. Regarding the 1955 beacon incident, Gabon argued that France's construction indicated a competing claim.  

Maritime Boundary Delimitation:  

Equatorial Guinea invoked the 1900 Convention as a legal title since it established the terminus of the land boundary in Corisco Bay. It also invoked the 1982 United Nations Convention on the Law of the Sea (UNCLOS) as a binding international convention relevant to the delimitation. Additionally, it referenced customary international law, specifically the principle that a State's title and entitlement to adjacent maritime areas derive from its title to land territory. 

Gabon invoked the "Bata Convention" as the only legal title having the force of law for maritime boundary delimitation. Alternatively, it contended that none of the alleged legal titles cited by Equatorial Guinea qualified as legal titles for the maritime boundary. 

Position on the "Bata Convention": 

Equatorial Guinea firmly argued that the "Bata Convention" does not have, and was never understood or treated as having, the force of law. It characterized the "Bata Convention" as, at most, "an agreement to continue to seek a final agreement". It stressed that the subsequent conduct of the Parties confirmed its non-binding nature.  

Gabon strongly asserted that the "Bata Convention" was a legally binding treaty and a valid legal title.It argued that the circumstances of its signing indicated the parties' intention to be legally bound. It contended that the subsequent conduct of parties to a treaty cannot call into question its terms. 

III. COURT’S REASONING AND CONCLUSION  

The International Court of Justice (ICJ) was tasked, under the Special Agreement, to determine whether the "legal titles, treaties and international conventions" invoked by the Parties have the force of law in their relations concerning these boundaries and island sovereignty. The Court broadly interpreted "legal titles" to encompass any source of rights to territory under international law. 

I. The "Bata Convention"(14-1) 

The Court found that the "Bata Convention" is not a treaty having the force of law in the relations between the Parties and does not constitute a legal title within the meaning of the Special Agreement. While the "Bata Convention" appeared at first sight to be a treaty, the Court noted that certain features, particularly Article 7 and a nota bene clause, cast doubt on the parties' intention to definitively establish boundaries as they made undertakings conditional on future agreements. The Court also observed that the information regarding the circumstances of its signing was limited and contradictory. Subsequent diplomatic correspondence was inconclusive. 

II. Land Boundary Delimitation (Unanimous) 

The Court unanimously found that the legal titles having the force of law for the delimitation of the common land boundary are the titles held by France and by Spain, based on the 1900 Convention, to which Gabon and Equatorial Guinea respectively succeeded. Regarding the Utamboni River area, the Court concluded that the proposal made by the 1901 Commission to modify the boundary was not approved through formal decisions by the Spanish and French Governments. It also found that Spain and France did not approve the proposal. Concerning the Kie River area, the Court determined that the 1919 Governors' Agreement did not modify the boundary described in Article IV of the 1900 Convention. This agreement was merely a temporary and provisional line. The Court, therefore, concluded that no modifications were made to the boundary described in Article IV of the 1900 Convention under its established procedures. 

III. Sovereignty over Mbanié/Mbañe, Cocotiers/Cocoteros, and Conga (13-2) 

The Court found that the legal title having the force of law for sovereignty over these islands is the title held by the Kingdom of Spain on 12 October 1968, to which the Republic of Equatorial Guinea succeeded. The Court considered these three islands to constitute a single unit. The Court's finding was based on an intentional display of authority by Spain that was continuous and uncontested. This was evidenced by: Spanish acts à titre de souverain: Before 1900, Spain acted as sovereign over Corisco Island and its "dependencies". The Court found that both Spain and France considered them "dependencies" of Corisco Island. 

French recognition was on the basis that:  

1. Maps: Contemporaneous French maps depicted Mbanié/Mbañe as part of Spanish colonial territory. 

2. 1900 Convention: While not a direct source of title, the 1900 Convention was considered consistent with Spain's claim over its dependencies. 

3. 1955 Beacon Incident: Internal French statements confirmed France's view that Cocotiers/Cocoteros was under Spanish authority. 

4. Post-independence effectivités: Equatorial Guinea maintained control after independence.  

France thus acknowledged Mbanié/Mbañe as a dependency of Corisco Island. 

IV. Maritime Boundary Delimitation (Unanimous) 

The Court unanimously found that the 1900 Convention constitutes a legal title within the meaning of the Special Agreement to the extent that it established the terminus of the land boundary, which serves as the starting-point of the maritime boundary. The Court also unanimously found that the 1982 United Nations Convention on the Law of the Sea (UNCLOS) is an international convention that has the force of law in the relations between the Parties, insofar as it concerns the delimitation of their maritime boundary. However, the Court clarified that UNCLOS is not itself the source of a right to specific maritime areas and therefore does not constitute a "legal title" in that specific sense. Lastly, the Court concluded that customary international law, specifically the principle that a state’s entitlement to adjacent maritime areas derives from its title to land territory, does not constitute a legal title within the meaning of the Special Agreement.