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A Straight Line Towards the Sea

A Comment on the Judgment in the case of Maritime Delimitation in the Indian Ocean (Somalia v. Kenya)


Almost to the day six months after the public hearings took place (for a comment see here), the International Court of Justice delivered its judgment in the case of Maritime Delimitation in the Indian Ocean (Somalia v. Kenya) on 12 October 2021. The judgment makes an important contribution to the law of acquiescence while showcasing the Court’s balanced approach in delimiting maritime boundaries. This post will focus on the concept of acquiescence and the reasons why the Court did not accept Kenya’s position in the case.

Position of the Parties and Summary of Holdings

Somalia had asked the Court to determine its maritime boundary with Kenya in accordance with the Convention on the Law of the Sea (UNCLOS) as it contended that no maritime boundary had yet been agreed on by the two States. Kenya argued that Somalia had agreed by acquiescence to a maritime boundary that follows the parallel of latitude at 1° 39’ 43.2’’.

Source: Maritime Delimitation in the Indian Ocean (Somalia v. Kenya), Judgment, ICJ Reports 2021, p. 18


The Court sided mostly but not entirely with Somalia: It found that Somalia had not acquiesced to Kenya’s claim (para. 36-89). It then delimited the maritime areas between the two States. Regarding the territorial sea (within 12 nm) it used the equidistance method, i.e., it drew a line every point of which is equidistant from the nearest points on the coastal baselines (Art. 15 UNCLOS). When drawing the equidistance line, the Court disregarded small islets which the Court saw would have disproportionately impacted the course of the line (para. 114). In delimiting the exclusive economic zone (EEZ) and the continental shelf within 200 nm, the Court could not rely solely on the equidistance method. Art. 74(1) UNCLOS and Art. 83(1) UNCLOS require an equitable agreement between the parties. In accordance with its previous jurisprudence, the Court applied a three-step-method: First, the Court drew a provisional equidistance line (Maritime Delimitation in the Black Sea (Romania v. Ukraine), para. 118). The Court then considered whether there were factors requiring an adjustment of this line (id. para. 120). The Court refuted several factors presented by Kenya such as security, access to fisheries, and oil concessions. It accepted Kenya’s argument that an unadjusted equidistance line would cause a significant cut-off effect which would substantially narrow Kenya’s maritime entitlements (para. 162-171). The reason for this cut-off-effect lies in the concave coastline of Somalia, Kenya, and Tanzania with Kenya being in the middle (cf. North Sea Continental Shelf (Germany v. Denmark/Netherlands), para. 91). The Court therefore adjusted the equidistance line in favour of Kenya. Lastly, the Court applied a disproportionality test ensuring there is no disproportion between the ratio of the lengths of the relevant coasts and the ratio of the respective shares in maritime areas (id. para. 213). The Court delimited the maritime boundary beyond 200 nm along the same adjusted line (para. 196). Several judges disagreed with the adjustment of the equidistance line, including former President of the Court Judge Yusuf, whose involvement as a Somali national had been criticised by Kenya.

Source: Maritime Delimitation in the Indian Ocean (Somalia v. Kenya), Judgment, ICJ Reports 2021, p. 71


The Court did not agree with Somalia’s argument that Kenya’s activities in the disputed maritime areas violated Kenya’s obligations to respect Somalia’s sovereignty and sovereign rights as Kenya’s actions occurred before the judgment was delivered and were carried out in good faith (para. 204).

The initial reception was expectedly divided: While Somalia’s President Mohamed Abdullahi Mohamed welcomed the Court’s decision, his Kenyan counterpart, President Uhuru Kenyatta, rejected the decision in its entirety reiterating Kenya’s position that the Court lacked jurisdiction over the matter. This does not alter the final and binding character of the judgment.

The Issue of Acquiescence

The maritime boundary between Somalia and Kenya would have been substantially different if the Court had accepted Kenya’s argument regarding acquiescence. Knowing that delimitation under UNCLOS would most likely favour Somalia, Kenya argued that the parties bilaterally agreed on a maritime boundary following the parallel of latitude by means of acquiescence. Kenya argued that it had continuously and for a significant time acted in a manner which indicated its view that its maritime boundary with Somalia followed the parallel of latitude.

The Court’s Standard to Establish Acquiescence

The Court first observed that UNCLOS provides that States may bilaterally agree on the delimitation of their maritime boundary. Such agreement need not necessarily be made in writing as long as a “shared understanding” between the States can be established (paras. 48-50). To establish a shared understanding, the Court observed, one may recur to the concepts of acquiescence and tacit agreement (paras. 51-52). The Court in line with its Gulf of Maine (Canada v. USA) and Land, Island and Maritime Frontier Dispute (El Salvador v. Honduras) judgments described acquiescence as “equivalent to tacit recognition manifested by unilateral conduct which the other party may interpret as consent”. Thus, the lack of protest by one State may be interpreted by another State as an acceptance of a legal claim. The Court stipulated two conditions for such an acceptance by acquiescence: First, a legal claim maintained by one State consistently and publicly over a significant period (Fisheries (UK v. Norway), p. 138-9). Secondly, lack of protest by the other State within a reasonable time and for a significant duration (Temple of Preah Vihear (Cambodia v. Thailand), p. 32). The Court emphasised that the conduct of the acquiescing State must indicate that State’s clear and consistent acceptance (Gulf of Maine (Canada v. USA), para. 145).

The Court applied the two concepts of acquiescence and tacit recognition in conjunction and without distinction. While both concepts describe the inference of consent to a legal claim from a certain conduct, they differ as to the required conduct. Acquiescence is based on inaction where action was called for, while tacit recognition is generally understood as positive action. In its early jurisprudence, the Court often relied on examples of inaction such as lack of protest or questioning of legal claims to establish acceptance (see Fisheries (UK v. Norway), Right of Passage (Portugal v. India), Temple of Preah Vihear (Cambodia v. Thailand)). In recent years, the emphasis has shifted towards examining positive conduct to prove acceptance (Maritime Dispute (Peru v. Chile). The application of both concepts in conjunction seems cogent. A State’s conduct is often a combination of action and inaction. An assessment of both kinds of conduct more aptly reveals a State’s true “state of mind”. This holds especially true for the delimitation of maritime boundaries which are both permanent and excessively important for economic, political, and military reasons. The standard of proof that a maritime boundary has been established by tacit agreement must consequently be strict (Territorial and Maritime Dispute in the Caribbean Sea (Nicaragua v. Honduras), para. 253).

No Consistent Claim by Kenya, no Consistent Acceptance by Somalia

Applying this standard, the Court assessed whether there was compelling evidence that Kenya had consistently claimed a maritime boundary at the parallel of latitude which had called for response by Somalia and whether there was compelling evidence that Somalia accepted Kenya’s claim.

The Court first considered the examples which Kenya identified as supporting its position. The first, a proclamation made by Kenya’s President in 1979, claimed a maritime boundary along a parallel of latitude. The Court dismissed this as proof, however, by juxtaposing it to Kenya’s 1972 Territorial Waters Act which continued in force in 1979 and which referred to a “Median line”. The Court also cited Kenya’s 1989 Maritime Zones Act, which similarly referred to an equidistance line as the boundary of the territorial sea and the need for an agreement between Kenya and Somalia regarding the delimitation of the EEZ (paras. 54-60). Similarly, another presidential proclamation made in 2005 and submissions made by Kenya to the Commission on the Limits of the Continental Shelf did not support Kenya’s argument either. Both communications referred to an agreement between the parties that was still pending. The Court consequently found that Kenya had made no consistent claim that the parallel of latitude constituted the maritime boundary between Kenya and Somalia (para. 71).

The Court then examined if Somalia had accepted Kenya’s (inconsistently held) claim (paras. 72-80). Somalia first mentioned the delimitation of its maritime boundary with Kenya in its 1988 Maritime Law in which it stated that the border with Kenya was “a straight line toward the sea from the land”. Both Somalia and Kenya argued that this supported their positions. The Court found that without further information the meaning of the sentence could not be determined. Somalia did not immediately react to Kenya’s 2005 proclamation. Yet, in 2009 it stressed on several occasions that its maritime boundary with Kenya had not yet been settled. Consequently, the Court found no compelling evidence that Somalia had acquiesced to the maritime boundary claimed by Kenya.

Concluding Remarks

The judgment emphasises the Court’s high standard of proof for establishing a maritime boundary by acquiescence. It seems unlikely that the mere absence of protest without any positive conduct indicating acceptance will suffice in future cases to prove acceptance of a certain maritime or territorial delimitation. The Court’s assessment of Kenya’s and Somalia’s domestic law also highlights the important interactions between domestic and international law.

Christoph Saake

Christoph Saake is a PhD candidate and research assistant at Bucerius Law School. His research focuses on the law of the United Nations and international adjudication.

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