1. Introduction
On 19 May 2025, the International Court of Justice (ICJ) delivered an important judgment pertinent to the law of treaties in the case concerning Land and Maritime Delimitation and Sovereignty over Islands. The proceedings had been instituted in 2021 by a Compromis, in which the Gabon and Equatorial Guinea jointly submitted to the ICJ a dispute regarding the delimitation of their common land and maritime boundaries, as well as sovereignty over the islands of Mbanié/Mbañe, Cocotiers/Cocoteros, and Conga. Notably, in this case, the World Court was requested to determine whether the legal instruments invoked by the parties possessed binding legal force in their bilateral relations. In this respect, Gabon relied on both the 1900 Franco-Spanish Convention and the 1974 Bata Convention. Equatorial Guinea, by contrast, relied only on the 1900 Convention. Notably, the Court was not tasked with delimiting boundaries or determining sovereignty directly. Instead, the special agreement entrusted the ICJ with assessing whether the instruments and titles invoked by each Party had the legal force in their bilateral relations. Central to this inquiry stood the so-called Bata Convention, a document Gabon submitted as a binding treaty concluded in 1974.
2. The Question of Intent
The Vienna Convention on the Law of Treaties, 1969 (VCLT) defines a treaty as an international agreement concluded between States in written form and governed by international law regardless of its designation. Over time, the interpretation of agreements may indeed give rise to different understandings, potentially resulting in complex disputes. In resolving such matters, international courts and tribunals are guided by the general interpretive framework laid down in the VCLT as reflection of customary international law. Notably, treaty interpretation is not a mechanical exercise, but an “art” informed by legal reasoning and especially context. As Kolb observes, interpretation resists rigid methodology; it involves the construction of persuasive understandings of a text in light of its object, purpose, and broader circumstances. The International Law Commission (ILC), in codifying these rules, rejected any strict hierarchy among interpretive elements. Instead, it emphasized a unified process grounded in the primacy of intention considering the sovereign equality of the States. This approach was duly reflected in Gabon v. Equatorial Guinea, where the Court declined to treat the Bata Convention as a binding instrument. In this regard, the ICJ did not rely on form alone, but assessed the absence of subsequent conduct and any clear indication of a mutual intention to be bound. Evidently, rather than any unilateral position, mutual intent defines the legal bond between the parties.
Interestingly, Gabon noted in its counter-memorial that during and immediately after the State visit to Equatorial Guinea in 1974 that Gabonese media covered the outcome of the negotiations in definitive terms. The Gabonese television reported that “everything is settled” quoting the then President of Gabon upon his return. A press release was also published in L’Union, a Gabonese newspaper, stating that the two Heads of State had signed Bata Convention, accompanied by a photograph of the signing ceremony. Gabon submitted this to the Court as indicative of a mutual intent to resolve boundary questions definitively. Be that as it may, while these affirmations may be relevant in evidentiary terms, they are not regarded as necessarily decisive elements of treaty formation in the present case. Arguably, had there been a joint press release of both States then perhaps it may serve as stronger indicator of a shared mutual understanding and would carry greater legal weight. Nonetheless, the absence of any such joint expression in 1974 further undermined Gabon’s assertion that the Bata Convention was ever treated as a binding instrument.
Article 31 of the VCLT provides that a treaty must be interpreted in good faith, according to the ordinary meaning of its terms, in their context, and in light of its object and purpose. That context includes the text, related agreements accepted by the parties, subsequent practice evidencing mutual understanding, and relevant rules of international law. Related to this, the Libya v. Chad judgment underscored the primacy of intent and recognition in boundary agreements. The ICJ held that the 1955 Treaty of Friendship and Good Neighborliness fixed the boundary by referencing colonial instruments, highlighting that mutual recognition of prior treaties could suffice, provided the intention to do so was clearly established. By contrast, in Gabon v. Equatorial Guinea, the Court found no such mutual recognition or consistent implementation of the 1974 Bata Convention. As it reiterated in Libya v. Chad, “the fixing of a frontier depends on the will of the sovereign States directly concerned.” The absence of such joint will, combined by Gabon’s prolonged silence, ultimately undermined its claim.
The search for the parties’ common intention frequently entails reference to preparatory work. While Article 32 of the VCLT formally treats such materials as supplementary, international courts have consistently rely on them. In this case, no such supplementary materials were submitted. In this respect, Equatorial Guinea highlighted the absence of any preparatory material, minutes of the meeting or official public statements that could be expected in the preparation of such a treaty. The Court therefore had no evidentiary basis to apply Article 32 and instead confined its analysis to the text and the conduct of the Parties (see ICJ Judgment, para. 61).
Article 11 of the VCLT affirms that a State's consent to be bound may be expressed through various means, including signature. Nevertheless, it presupposes that such consent is clearly and mutually intended. According to Fitzmaurice, the determinative factor remains the mutual intention of the parties. In the present case, Gabon invoked a document allegedly signed in 1974 and invoked the principle of pacta sunt servanda. While the Court assumed, without deciding, that a document had been signed in Bata in 1974, it found no evidence that either party ever treated it as a binding treaty. Yet, the mere existence of a signed text, absent evidence of intention to be legally bound, was insufficient to meet the threshold of treaty formation. As Article 11 itself states, no legal obligations can arise without clear and mutual consent. The Court thus concluded that the so-called Convention failed to satisfy the foundational criteria of treaty formation. The absence of ratification, invocation, or any consistent affirmation placed the instrument outside the realm of the law of the treaties.
Remarkably, the text itself contained qualifying clauses that cast doubt on its finality. Notably, Gabon acknowledged that it could not locate the original of the Bata Convention in its archives, attributing this to poor record keeping caused by adverse climate conditions and limited technical capacity. Nevertheless, Gabon managed to submit a certified copy obtained from the French Ministry of Foreign Affairs. It comprises ten articles on territorial exchanges, recognition of sovereignty over specific islands, and reciprocal access to territorial waters. However, Articles 7 and 8 explicitly envisaged subsequent protocols to define the precise boundaries of the exchanged land and to set out procedures for implementation. Naturally this indicated that several key provisions remained unsettled in 1974. Moreover, a nota bene beneath the signatures stipulated that Article 4, concerning the maritime boundary, was to be revised to conform to the 1900 Convention. These textual qualifying elements requiring further negotiation and revision appear to suggest that the instrument lacked the definitive and unconditional character of a legally binding instrument. As Equatorial Guinea rightly argued in its reply, an instrument that is neither followed up, invoked, nor implemented cannot constitute a treaty within the meaning of international law.
Judge ad hoc Wolfrum observed that even if the Bata Convention had been signed, the conditional nature of its provisions deprived it of substantive legal effect. On the other hand, Judge ad hoc Pinto argued that the document’s UN registration, formal language, and structure merited greater legal weight.
The invalidity of a treaty presupposes that a treaty exists in the first place. As McNair noted, the mere act of signing does not render an instrument binding; validity depends on clear and mutual intent. In Gabon v. Equatorial Guinea, the ICJ echoed this view. Despite Gabon’s argument of the so-called Bata Convention as a treaty, the Court found no confirming evidence. In the absence of such clear intent or consistent conduct, the document lacked the basic elements of treaty formation. The Court thus treated the matter as one of non-formation, not invalidity.
3. State Practice and Silence
Equatorial Guinea’s claim rested on a colonial title inherited from Spain. Through the 1900 Convention between Spain and France, the 1901 Franco-Spanish Delimitation Commission, and a series of administrative and diplomatic acts, Spain’s sovereignty over the islands was consistently exercised and remained uncontested until Equatorial Guinea’s independence in 1968. In its Memorial and subsequent pleadings, Equatorial Guinea reconstructed a legal chain of title, supported not only by treaties but also by subsequent conduct, namely, administrative practice in the form of Spanish decrees, military presence, censuses, and diplomatic correspondence. The Court accepted this succession as valid.
One of the most salient aspects of this judgment is the Court’s treatment of State conduct, not only in terms of what the Parties did, but in what they failed to do. For nearly thirty years, neither Gabon nor Equatorial Guinea acted in a manner consistent with the existence of a binding treaty. There was no implementation of the Bata Convention, no reliance on its terms in diplomatic correspondence, and no invocation during negotiations. As Equatorial Guinea observed: Gabon neither implemented the agreement nor invoked it in diplomatic exchanges with Equatorial Guinea, and did not treat it as binding legal instrument for almost three decades.
At the heart of this dispute lied the binding nature of the Bata Convention. The Court treated the prolonged silence not as neutral, but as indication of the absence of a binding commitment. As Judge Aurescu noted in his declaration, the Court could have stated more explicitly that the very existence of the Bata Convention remained uncertain.
4. Conclusion
In conclusion, the ICJ’s judgment in Gabon v. Equatorial Guinea authoritatively reaffirms core principles of the law of treaties: form of an instrument alone, without mutual intent and consistent conduct, cannot create legal obligations. As such treaties are formed not by presumption, but by intention and actual performance in practice. The Court’s emphasis on intent and corresponding conduct can indeed offer guidance for similar disputes involving instruments with unclear status. Finally, the ruling further confirms that post-colonial succession can serve as a valid legal basis for sovereignty, provided that the original title was lawfully held and clearly transferred.
Dr. Murat Sümer is the Nippon Foundation Lecturer in International Maritime Law at the IMO International Maritime Law Institute in Malta. He is an international maritime lawyer, former diplomat, and academic specializing in the law of the sea, maritime boundary delimitation, and peaceful settlement of maritime disputes.
