Pushing the Boundaries? Maritime Delimitation and evolving ICJ jurisprudence on International Law of the Sea

Maritime delimitation is the process that involves “establishing lines separating from each other the maritime areas in which coastal states exercise sovereignty or jurisdiction”.[1] It is one of the most extensively researched fields in international law. The understanding of the delimitation process lies at the intersection of legal and spatial analysis. The International Court of Justice (ICJ) delivered its landmark ruling in Somalia v. Kenya concerning the dispute of “Maritime Delimitation in the Indian Ocean” on October, 12, 2021. This article aims to explore the legal, geographical and political implications of the decision.

Historical Background

Boundaries are man-made and a political phenomenon. They are more so at sea, than on land, because maritime boundaries have no natural character. As former ICJ judge Bedjaoui exquisitely noted: “Having always shunned land relief despite the fact that it is visible, man cannot but shun still more underwater relief which is out of his sight.”

The regime of the high seas, including the continental shelf were the priority topics in the first conference of the International Law Commission (ILC) and its travaux preparatoires, which led to the 1958 Geneva Conventions. The central theme of the conference as regards to the delimitation of maritime zones was the quest for a material criteria. This quest resulted in all the provisions of the subsequent 1982 UNCLOS relating to maritime delimitation, embodying the “equidistance principle”. The three provisions of the UNCLOS—Articles 15, 74(1) and 83(1), form the backbone of the legal framework in maritime delimitation. Maritime delimitation disputes in the past include the famous Grisbadarna Arbitration, North Sea Continental Shelf Cases, Anglo-French Arbitration, Dubai/Sharjah Arbitration, Tunisia/Libya Case, Romania/Ukraine Case and the Gulf of Maine Case.

The Dispute

Both Somalia and Kenya are neighboring countries with a shared boundary which intersects at the Indian Ocean in the south-east. This maritime zone holds vast oil and gas reserves which are a bone of contention for both the states. Both countries have ratified the 1982 UNCLOS and are bound by it. In 2009, both countries signed a MoU in which they agreed to a maritime delimitation process in the future by negotiations, however the Somalian legislature later rejected this. In 2012, the Kenyan government awarded several offshore exploration blocks to foreign oil companies in the disputed zone. The Somalian government contended that this was a violation of its continental shelf and Exclusive Economic Zone (EEZ).

Both the states have applied a complete opposite approach to the delimitation process. Somalia contended that the maritime boundary should run a parallel path in the south-east direction along the countries’ land borders. Pursuant to the UNCLOS provisions, such an approach would yield an equidistance line through the maritime areas as required by international law. Somalia requested the ICJ to declare all hydrocarbon exploration activities by Kenya in the disputed zone as a violation of its territorial sovereignty and a breach of obligations under the UNCLOS and customary international law.

On the flip side, Kenya argued that both states had already agreed to a maritime boundary line which runs parallel to the latitude. Taking this approach, Kenya contended that the boundary line should take a 45-degree bend at the coastline to make it parallel to the latitudinal line. This would eventually give Kenya control over a much larger piece of the disputed maritime zone. Kenya also argued that Somalia had acquiesced to such an approach, which was tantamount to tacit agreement.

The Ruling

The ICJ rejected Kenya’s claim that both states had, through tacit agreement, established a maritime boundary which ran parallel to the latitudinal line. Kenya’s claim was founded on the premise that Somalia had failed to protest for a prolonged time to such a boundary line of the territorial sea, EEZ and the customary extended continental shelf within 200nm. Moreover, this boundary line was consistent with both countries’ practices vis-à-vis fisheries, naval patrols, oil & gas exploration and scientific research. The Court held that there was no compelling evidence to establish a tacit agreement, which must be “more than the demonstration of longstanding oil practice or adjoining oil concession limits”. It concluded that no agreement had been reached on a ‘de-facto maritime boundary’.

In addition to this, the court applied the usual “equidistance principle” methodology to determine maritime boundary delimitation. The ruling was an effort to maintain consistency with the existing case-law and the relevant provisions of the UNCLOS. The decision noted that in absence of compelling factors, there was no reason to depart from its “usual practice”. The court employed the long-standing and existing procedure. Firstly, it identified the coastlines and baselines and the extent of any entitlements that overlap. Secondly, the delimitation of the territorial sea was done using the median-line rule. Finally, the court proceeded to delimit the EEZ and the continental shelf within and beyond the 200nm.

The ‘equidistance principle’ methodology is not compulsory under the 1982 UNCLOS, but as the decision noted: “Since the adoption of the Convention, the Court has gradually developed a maritime delimitation methodology to assist it in carrying out its task.” In using the methodology, a provisional equidistance line is drawn from appropriate base points (used as reference points) from the coast. This is done objectively and in such a manner that the result obtained is equitable. In the present case, the court strictly adhered to geographic factors and rejected Kenya’s assertions of any political, strategic or economic factors to be considered in making an adjustment. The only adjustment that the court made was on the basis of concavity of the shoreline. This concavity of the shoreline has resulted in an inequitable delimitation which was highlighted by the separate opinions of three judges (Abraham, Yusuf and Robinson). The court also employed a retrospective proportionality test to verify the fairness of the adjusted equidistance line. The results found that the ratio between the maritime areas which pertain to Kenya and Somalia was 1:1.3 in favor of Kenya.

The implications

The role of non-geographical factors in influencing the maritime delimitation process has been a hot topic among international law experts. Political and economic aspects are the most important motivators of maritime boundary disputes, and are the crux of concepts like continental shelf, EEZ and territorial seas. The ICJ has not considered these dimensions in its maritime delimitation jurisprudence. It is now well-settled that non-geographical factors do not play a significant role in employing the delimitation methodology of maritime zones. However, the ICJ has not explicitly stated that such considerations are irrelevant or cannot be invoked in the future. Interestingly, the ruling highlighted that “relevant circumstances are factors which are mostly geographical in nature, but that there is no closed list of relevant circumstances”.

Similar to the ‘International Tribunal for the Law of the Sea’ (ITLOS) ruling in Bangladesh v. Myanmar, the ICJ also maintained its jurisdiction in the present dispute, notwithstanding the absence of recommendations from the ‘Commission on the Limits of the Continental Shelf’ (CLCS) pertinent to delimitation beyond 200nm. This was also consistent with ICJ’s previous ruling in Nicaragua v. Colombia, where the court had upheld its jurisdiction to delimit the maritime zone beyond 200nm on the basis of scientific data submitted to CLCS, although the commission had not yet issued its recommendations. In the present case, President Donoghue expressed her reservations on this issue in her separate opinion and Judge Robinson also criticized the Court’s decision to proceed with delimitation beyond 200 nm.

Another key aspect of the case was the ongoing seismic and drilling activity being conducted by Kenya in the disputed maritime area while the case was pending adjudication. Somalia had alleged that Kenya’s unilateral activities in the zone constituted a breach of Articles 74(3) and 83(3) of UNCLOS and a violation of its sovereignty. Legal experts argue that Somalia had correctly argued the possible infringement of its sovereign rights. However the ruling rejected the claim and relied on the ITLOS decision in the Ghana v. Côte d’Ivoire case. It held that any unilateral activities carried out by a State in a disputed maritime area to which another State has also laid claims do not violate the latter’s sovereignty, even if the area is later allocated to that State. Moreover, the court evinced that activities of a ‘transitory character’ (i.e. granting of oil contracts or performance of seismic surveys) did not suffice to jeopardize the reaching of a final agreement. But the court emphasized that unilateral drilling in disputed maritime areas causing permanent harm to the marine environment did attract the state obligations pursuant to Articles 74(3) and 83(3) of UNCLOS, as held in Guyana v Suriname. However, that was not the case in the instant dispute.


The judgment shows a desire by the ICJ to contribute to the continuum of consistent delimitation jurisprudence by maintaining that the ‘equidistance/relevant conditions method’ is now a standard in the maritime delimitation process. It also underscores the importance of material criteria associated with coastal geography, such as concavity and coastal length while disregarding non-geographical factors related to unilateral activities in the disputed maritime area. However, there are still inconsistencies and discrepancies in the ICJ’s ruling. As noted, the decision considered concavity outside the relevant coastlines; delimited the continental shelf beyond 200 nm despite the absence of recommendations by the CLCS; and confusingly held on to the view that delimitation is constitutive of sovereignty. It is pertinent to note that the courts and tribunals under Part XV of the UNCLOS have failed to reach a consensus about which stage of the proceedings the absence of the CLCS’s recommendations should be considered. The disagreement by the four judges (Robinson, Xue, Yusuf and Abraham) in their opinions pertinent to the way the Court adjusted the provisional median line within 200nm is also noteworthy. Judge Yusuf aptly highlighted in his separate opinion that it “may also lead in the future to a Court-created new problem between the Parties”, for example encroaching the sea-bed area”.

[1] Caflisch, Lucius. “Maritime Delimitation Disputes—What Modes of Settlement?.” In The Hamburg Lectures on Maritime Affairs 2009 & 2010, pp. 69-87. Springer, Berlin, Heidelberg, 2012.

Tanzeel ur Rehman
Tanzeel ur Rehman
Tanzeel ur Rehman is an undergraduate law student at University of Sindh, Pakistan. He has a passion for creative and legal writing. He aspires to be an International lawyer.