DISPUTE CONCERNING DELIMITATION OF THE MARITIME BOUNDARY  BETWEEN GHANA AND CÔTE D’IVOIRE IN THE ATLANTIC OCEAN.

CASE TITLE & CITATION

Full Name: Dispute Concerning Delimitation of the Maritime Boundary between Ghana and  Côte d’Ivoire in the Atlantic Ocean (Special Chamber of ITLOS, Case No. 23) Official Citation: [2017] ITLOS Rep 4 (Judgment on Merits, 23^rd September 2017); [2015]  ITLOS Rep 146 (Provisional Measures Order, 25 April 2015) itlos.org

COURT NAME & BENCH

• Court: International Tribunal for the Law of the Sea (ITLOS), Ad Hoc Special Chamber, Hamburg
• Judges: President Boualem Bouguetaia, Judges Rüdiger Wolfrum, Jin-Hyun Paik, with ad hoc Judges Thomas A. Mensah (appointed by Ghana) and Ronny Abraham (appointed by Côte d’Ivoire)
• Bench Type: Ad Hoc Special Chamber

DATE OF JUDGMENT

The final ruling was rendered on 23^rd of September 2017 itlos.org

PARTIES INVOLVED

• Applicant: Republic of Ghana, which claimed that a maritime boundary already existed through a customary application of an equidistance line based on offshore oil concession practice, specifically along the median line emanating from Boundary Pillar 55. Ghana  asserted this boundary extended both within and beyond 200 nautical miles itlos.org.
• Respondent: Republic of Côte d’Ivoire, which denied any pre-existing maritime boundary. Côte d’Ivoire supported the use of the angle-bisector method for delimitation at approximately 168.7° azimuth, reasoning this would better accommodate its concave coastline. Côte d’Ivoire further argued that Ghana’s unilateral oil exploration encroached  upon its sovereign rights under UNCLOS Articles 77 and 83 and violated provisional  measures imposed by ITLOS in 2015 Fietta Law.

FACTS OF THE CASE

The contested area lies in the Gulf of Guinea, known for substantial hydrocarbon deposits ASIL  Insights. Ghana’s Jubilee (2007) and TEN oil fields are located across the as-yet undefined median  line, with Total also making substantial discoveries, around 2 billion barrels of oil and 1.2 trillion  cubic feet of gas, just east of Jubilee. Reuters.

Since Ghana’s independence (1957) and Côte d’Ivoire’s (1960), no formal maritime boundary had  been agreed despite overlapping concession claims.

• Core Dispute:

Ghana asserted the existence of a customary equidistance boundary along an azimuth of  approximately 168° from Boundary Pillar 55, supported by decades of aligned oil  concession blocks and maps Fietta Law.

Côte d’Ivoire rejected such claims, highlighting longstanding protests predating  substantial oil discoveries, and contended that the equidistance method would unfairly  truncate its concave coastline ASIL Insights.

Following failed bilateral talks, Ghana initiated Annex VII arbitration in 2014; however, on  December 3^rd, 2014, both countries consented to move the dispute to a Special Chamber of ITLOS. [itlos.org]. Soon after, in February 2015, Côte d’Ivoire requested provisional measures under  UNCLOS Article 290(1), aiming to halt Ghana’s drilling activities in the disputed area due to  environmental concerns and claims of infringement of its rights itlos.org, Fietta Law.

ISSUES RAISED

• Jurisdiction: Whether the issue concerned the Special Chamber’s jurisdiction to establish the maritime boundary beyond 200 nautical miles and to rule on Côte d’Ivoire’s counterclaims related to Ghana’s purported violations of UNCLOS. Fietta Law, itlos.org.
• Presence of an Agreement / Estoppel: The consideration of whether a tacit or customary maritime boundary had been established through prolonged state practice and if Côte d’Ivoire was legally barred from disputing the boundary. ASIL Insights.
• Delimitation Method: Whether the boundary should be determined strictly using equidistance (with potential adjustment for relevant circumstances), or by application of the angle-bisector method; and whether coastal concavity or Ghana’s resource activities  constituted special circumstances justifying deviation from equidistance.
• State Responsibility: Whether Ghana’s independent oil operations infringed upon Côte d’Ivoire’s sovereign rights or its duty to negotiate in good faith as outlined in UNCLOS Articles 77 and 83(1)– (3), and whether Ghana failed to comply with the provisional  measures order issued in 2015.

ARGUMENTS OF THE PARTIES

• Ghana:

1. Emphasized more than five decades of consistent oil concession blocks, national  laws, and maps delineating an equidistance line from Boundary Pillar 55,  contending that these elements formed a modus vivendi between the involved  parties. ASIL Insights.
2. Advocated the equidistance method as the presumptive rule under UNCLOS,  emphasizing its geographic appropriateness and acceptance in principle by both  parties itlos.org, Fietta Law.
3. Denied any breach of the law or provisional measures relating to resource  exploitation, asserting all activities were in Ghana’s lawful maritime area and  undertaken in good faith.

• Côte d’Ivoire:

1. Rejected the presence of any implicit maritime boundary, citing several official  protests in 1992, 2009, and 2011 that challenged Ghana’s equidistance assertions. itlos.org, ASIL Insights.
2. Supported delimitation via the angle-bisector method at approximately 168.7°  azimuth, arguing that the equidistance approach would unfairly “cut off” its  maritime projection due to coastal concavity itlos.org, Fietta Law.
3. Alleged Ghana’s unilateral drilling violated Côte d’Ivoire’s sovereign rights in the  continental shelf (UNCLOS Arts. 77, 81), breached the good-faith negotiation duty  (Art. 83(3)), and disregarded the provisional measures order; sought reparations for  damages Fietta Law.

JUDGMENT / FINAL DECISION

In its unanimous decision issued on 23^rd September 2017, the ITLOS Special Chamber concluded  the dispute with the following resolution:

Jurisdiction: The Chamber recognized its authority to delineate the maritime borders between  Ghana and Côte d’Ivoire in all applicable sea areas, encompassing the territorial sea, the Exclusive  Economic Zone (EEZ), and the continental shelf beyond the 200-nautical-mile limit. Additionally,  it held the power to consider Côte d’Ivoire’s accusations against Ghana, given that these matters  were intrinsically connected to the boundary delimitation process. Fietta Law.

Tacit Agreement and Estoppel: The Special Chamber ruled that no tacit maritime boundary  agreement existed, nor was Côte d’Ivoire estopped from contesting the boundary. The Chamber  emphasized the stringent standard required to prove a tacit boundary, that there must be  “compelling evidence” demonstrating mutual intent itlos.org. While acknowledging the existence  of longstanding oil concession patterns, the Tribunal agreed with Côte d’Ivoire’s position that such  concession practices alone do not amount to binding boundary agreements. The Chamber noted  multiple formal Ivorian objections and extensive bilateral negotiations between 1988 and 2014, all  of which treated the boundary as still unsettled itlos.org. To reinforce its reasoning, the Tribunal  invoked the ICJ precedent of Nicaragua v. Honduras (2007), cautioning against inferring tacit  boundaries absent explicit treaties. Accordingly, Ghana’s submission of oil maps and coastal  submissions to the Commission on the Limits of the Continental Shelf (CLCS) were not deemed  sufficient proof of a binding maritime boundary itlos.org.

Delimitation Method: The Chamber applied the well-established three-step method involving the  construction of a provisional equidistance line, assessment of any relevant circumstances, and  application of a proportionality test, reflecting precedents such as the Black Sea delimitation itlos.org. The provisional equidistance line was drawn starting from Boundary Pillar 55+  (coordinates 05°05′23.2″N, 03°06′21.2″W) itlos.org. The Tribunal found no relevant  circumstances sufficient to justify adjustment of this line: coastal concavity, while present, was not  severe enough to warrant departure from equidistance, and the presence of oil deposits was deemed  irrelevant unless their loss would cause catastrophic harm itlos.org. The proportionality test  confirmed the fairness of the delimitation, allocating approximately 65,881 square kilometers  (35%) to Ghana and 132,842 square kilometers (65%) to Côte d’Ivoire, the ratio reflecting Côted’Ivoire’s significantly longer coastline itlos.org. The final maritime boundary was specified by  turning points A to F and a geodetic line extending seaward (azimuth 191°38′06.7″), with no  deviation from the provisional equidistance line itlos.org.

State Responsibility: Concerning Côte d’Ivoire’s allegations that Ghana infringed upon its  sovereign rights, the Tribunal found no evidence of any violation. Ghana’s activities related to  hydrocarbon exploration and drilling were carried out in good faith and occurred within the area  ultimately determined to belong to Ghana. The Tribunal also ruled that Ghana did not breach its  obligation to negotiate in good faith under UNCLOS Article 83(3) nor the provisional measures  order. Since after delimitation Ghana legally exercised rights over its portion of the continental  shelf, this did not constitute unlawful encroachment itlos.org, Fietta Law. Ghana was found to have  complied with the provisional measures order, including suspension of new drilling operations.  Consequently, no damages were awarded, and each party was ordered to bear its own legal costs.

LEGAL REASONING / RATIO DECIDENDI

The Tribunal’s reasoning highlighted several important principles:

• Stringent Evidentiary Standard: The Chamber stressed that the establishment of maritime boundaries requires clear and convincing evidence, echoing the ICJ’s approach in Nicaragua v. Honduras (2007). It rejected the notion that long-standing oil concessions  or unilateral acts could substitute for explicit mutual agreement on boundaries itlos.org.
• Equidistance and Relevant Circumstances: The decision reaffirmed the three-step process for maritime delimitation customary under international law: first drawing a provisional equidistance line; then considering any relevant geographic or other  circumstances that might justify adjustment; and finally performing a proportionality  review to avoid inequity or disproportion. itlos.org Economic factors such as proximity tohydrocarbon fields were deemed irrelevant unless the affected party could show  catastrophic consequences, an evidentiary bar not met here itlos.org.
• Unilateral Resource Activities during Disputes: Citing precedents like Nicaragua v. Colombia and the M/V Louisa case, the Tribunal recognized that coastal States may undertake resource activities in areas they consider under their jurisdiction pending final  delimitation, provided such activities are conducted in good faith and do not prejudice  negotiations under UNCLOS Article 83(3) itlos.org, Fietta Law.
• Environmental Duty: The provisional measures order balanced the need to protect the marine environment (pursuant to UNCLOS Article 192) with the competing economic interests, mandating cooperation between Parties for monitoring and environmental  safeguards during the delimitation process itlos.org.

CONCLUSION / OBSERVATIONS

The ITLOS Special Chamber’s decision definitively resolved a protracted maritime boundary  dispute in West Africa by applying and reinforcing the primacy of the equidistance principle in  maritime delimitation absent exceptional circumstances. The judgment imposed a high evidentiary  threshold to establish tacit boundaries through State practice, rejecting reliance on concession  maps alone. It clarified that good-faith resource exploitation in disputed waters is permissible  where it does not undermine negotiation or final delimitation agreements. The ruling thereby offers  a balanced framework promoting legal certainty, environmental stewardship, and peaceful  management of maritime resources between neighboring States. This outcome enables Ghana and  Côte d’Ivoire to proceed with development or cooperative management of their newly defined  maritime zones, resolving a dispute that had considerable regional economic and political  significance.

REFERENCE(S):

• ITLOS Judgments/Orders: Dispute Concerning Delimitation of the Maritime Boundary between Ghana and Côte d’Ivoire in the Atlantic Ocean (Special Chamber, Judgment, 23 Sept 2017) [2017] ITLOS Rep 4 https://www.itlos.org/fileadmin/itlos/documents/cases/case_no.23_merits/23_published_t exts/C23_Judgment_20170923.pdf itlos.org.
• ITLOS Provisional Measures: Dispute Concerning Delimitation of the Maritime Boundary between Ghana and Côte d’Ivoire in the Atlantic Ocean (Special Chamber, Provisional Measures Order, 25 Apr 2015) [2015] ITLOS Rep 146 https://www.itlos.org/fileadmin/itlos/documents/cases/case_no.23_prov_meas/23_publish ed_texts/2015_23_Ord_25_Avr_2015-E.pdf itlos.org.
• United Nations Convention on the Law of the Sea 1982, 1833 UNTS 397 (Arts 15, 74– 77, 83).
• Maritime Delimitation in the Black Sea (Romania v Ukraine) [2009] ICJ Rep 61; Territorial and Maritime Dispute (Nicaragua v Honduras) [2007] ICJ Rep 659; Territorial and Maritime Dispute (Nicaragua v Colombia) [2012] ICJ Rep 624.
• Joe Bavier, “Total finds Ivory Coast oil next to Ghana’s Jubilee”, Reuters (25 April 2013) https://www.reuters.com/article/total-ivorycoast-idUSL6N0DC3G220130425 reuters.com.
• Pieter Bekker & Robert van de Poll, ‘Ghana and Côte d’Ivoire Receive a Strict Equidistance Boundary’ (2017) 21(11) ASIL Insightshttps://www.asil.org/insights/volume/21/issue/11/ghana-and-cote-divoire-receive-strict equidistance-boundary asil.org.
• Fietta Law, ‘ITLOS Special Chamber delivers its judgment on the delimitation of the maritime boundary between Ghana and Côte d’Ivoire’ (Firm News, 23 Sept 2017) https://www.fiettalaw.com/pil_news/itlos-special-chamber-delivers-its-judgment-on-the delimitation-of-the-maritime-boundary-between-ghana-and-cote-divoire/ fiettalaw.com.