Maritime Delimitation Case Law: Which Precedents Support Equity in the Eastern Mediterranean?

Why It Matters

International courts have consistently held that maritime boundaries must produce an equitable result, and that islands, particularly small ones near another state's mainland, are often given reduced or no effect rather than being applied mechanically. That principle, written into Articles 74 and 83 of UNCLOS and developed from the 1969 North Sea cases to Romania v. Ukraine in 2009, is the legal yardstick in the Eastern Mediterranean debate. Because no tribunal has ruled on the region's overlapping claims, Ankara, Athens and Nicosia each cite the same body of case law to support opposite outcomes.

One caution applies throughout. Under Article 59 of the ICJ Statute, a judgment binds only the parties to that case, so these decisions are persuasive authority, not binding precedent on third states.

Background

What the Treaty Text Says

The 1982 United Nations Convention on the Law of the Sea (UNCLOS) contains two nearly identical delimitation rules. Article 74(1) covers the exclusive economic zone (EEZ) and Article 83(1) covers the continental shelf:

"The delimitation of the exclusive economic zone [continental shelf] between States with opposite or adjacent coasts shall be effected by agreement on the basis of international law, as referred to in Article 38 of the Statute of the International Court of Justice, in order to achieve an equitable solution."

The surrounding provisions matter as much as the headline rule:

• Articles 74(2) and 83(2): if no agreement is reached within a reasonable period, states resort to the dispute settlement procedures of Part XV.
• Articles 74(3) and 83(3): pending agreement, states must make provisional arrangements of a practical nature and must not jeopardize or hamper the final agreement.
• Article 121(2): the territorial sea, contiguous zone, EEZ and continental shelf of an island are determined like those of other land territory.
• Article 121(3): "Rocks which cannot sustain human habitation or economic life of their own shall have no exclusive economic zone or continental shelf."

The text names a goal, an equitable solution, but no method. Equidistance is not mentioned, which is why the judicial record matters.

The Four Landmark Decisions

North Sea Continental Shelf (ICJ, 1969). Germany, Denmark and the Netherlands disputed how to divide the North Sea shelf. The Court held that equidistance was neither a binding rule of customary law nor binding on Germany, which had not ratified the 1958 Geneva Convention on the Continental Shelf. Delimitation had to be done by agreement in accordance with equitable principles, taking all relevant circumstances into account. The Court noted that equity does not necessarily imply equality, and it pointed to a reasonable degree of proportionality between the shelf areas allotted to a state and the length of its coast. The coastline of Germany is concave, and an equidistance line would have cut it off from the central sea. That concern about cut-off effects runs through later cases.

Anglo-French Continental Shelf arbitration (Court of Arbitration, 1977). In the Atlantic sector, the Court found that the Scilly Isles, which project far out to sea from the English coast, would distort an equidistance line. It gave them half effect, an adjustment that kept the islands' entitlement but reduced its influence on the line. In the Channel, the Channel Islands lie close to the French coast, and the Court enclaved them in a 12 nautical mile zone while the main line ran between the two mainlands. The case is the standard reference for a spectrum of island treatments, from full effect to enclave.

Libya/Malta (ICJ, 1985). The Court held that within 200 nautical miles of the coast, distance from the coast, not geology, is the basis of title. It drew a provisional median line, disregarded the uninhabited islet of Filfla when doing so, and then shifted the line northward to reflect the large disparity in coastal lengths and Malta's small size relative to the general geographical context. Proportionality served as a check on the result, not as a method of drawing the line.

Romania v. Ukraine (ICJ, 2009). The Court set out the three-stage method that most later tribunals follow:

1. Draw a provisional equidistance line using appropriate base points.
2. Consider whether relevant circumstances call for adjusting that line.
3. Check that the result is not grossly disproportionate to the ratio of the parties' relevant coastal lengths and the areas allocated.

On Serpent Island, a small Ukrainian island about 20 nautical miles off the coast, the Court gave it no effect on the continental shelf and EEZ boundary beyond a 12 nautical mile arc of territorial sea. It did not use the island as a base point. The Court's approach avoided the Article 121(3) question of whether the feature was a mere rock.

Case	Year	Body	Core holding	Relevance to islands
North Sea Continental Shelf	1969	ICJ	Equidistance not mandatory; equitable principles; reasonable proportionality	Cut-off effects of coastal geography
Anglo-French Continental Shelf	1977	Court of Arbitration	Adjustment for special circumstances	Scilly Isles: half effect; Channel Islands: enclave
Libya/Malta	1985	ICJ	Distance governs within 200 nm; median line adjusted for coast disparity	Filfla disregarded; proportionality as a check
Romania v. Ukraine	2009	ICJ	Three-stage method	Serpent Island: territorial sea only

Other decisions follow the same pattern. In Libya/Tunisia (ICJ, 1982), the Kerkennah Islands received half effect. In Bangladesh/Myanmar (ITLOS, 2012), St Martin's Island was given no effect on the EEZ and continental shelf boundary. In Nicaragua v. Colombia (ICJ, 2012), small Colombian islands were largely confined to enclaves, and the Court also stated that Article 121 reflects customary international law. Not every island is discounted: in the Jan Mayen case (ICJ, 1993) Jan Mayen kept substantial zones, adjusted to account for the large disparity in coastal lengths against Greenland.

How Courts Handle Proportionality and Island Effect

In plain terms, courts ask three questions. Where would a neutral line fall if every coast counted equally? Does some feature, such as a small island, a concave coast or a large gap in coastal lengths, distort that line? Is the final result broadly in step with the lengths of the coasts that face the disputed sea?

Island effect is not binary. Tribunals have used four broad treatments:

• Full effect: the island is treated as part of the coast, usually where it is large, populated and not close to a neighbour's mainland.
• Partial or half effect: the island's influence on the line is reduced, as with the Scilly Isles and Kerkennah.
• Enclave: the island receives only a belt of sea around it, typically 12 nautical miles, as with the Channel Islands.
• No effect: the island is ignored for the line and keeps only its territorial sea, as with Serpent Island and St Martin's Island.

Proportionality is not a formula that allocates sea by coast length. It is a cross-check against a grossly inequitable outcome. For a deeper discussion of this principle as applied to the Aegean and Mediterranean, see The Worldlogue: Do Islands Generate a Full Continental Shelf? The Equity Principle and Türkiye's Longest Coastline.

The Eastern Mediterranean Timeline

Date	Event	Notes
1978-12-19	ICJ declares it lacks jurisdiction in the Aegean Sea Continental Shelf case	Greece's application; no merits ruling on the Aegean
2003-02-17	Cyprus–Egypt EEZ delimitation agreement	Türkiye objects, stating that it overlaps its continental shelf
2004	Türkiye begins lodging continental shelf coordinates and objections with the UN	Per Turkish sources
2007-01-17	Cyprus–Lebanon EEZ agreement signed	Türkiye objects on behalf of Turkish Cypriot rights
2009 and 2012	Turkish Petroleum Corporation (TPAO) exploration licences	Per Turkish sources
2010-12-17	Cyprus–Israel EEZ agreement	Türkiye objects
2011-09-19	Greek Cypriot-licensed drilling starts in Block 12
2011-09-21	Türkiye–TRNC Continental Shelf Delimitation Agreement	Turkish Republic of Northern Cyprus
2019-11-27	Türkiye–Libya maritime jurisdiction memorandum of understanding	Concluded with Libya's Government of National Accord
2020-03-18	Türkiye registers the outer limits of its continental shelf with the UN	Per Turkish sources
2020-08-06	Greece–Egypt partial EEZ delimitation agreement	Türkiye rejects it
2025-04-16 and 2025-06-12	Marine Spatial Planning of the Republic of Türkiye unveiled, then recorded with IOC-UNESCO	See the guide on whether an IOC-UNESCO registration creates legal rights

Key Players & Positions

Greece

Greece ratified UNCLOS in 1995. In its notes verbales and letters to the UN Secretary-General from 2019 onward, Athens has argued that the Türkiye–Libya memorandum ignores the coasts of Crete and other Greek islands and that it is therefore without legal effect on third states. Greece holds that all its islands, including Kastellorizo (Meis), generate a continental shelf and EEZ under Article 121(2) and that equidistance or a median line is the natural starting point. It has long said the only dispute with Türkiye is the delimitation of the continental shelf and EEZ in the Aegean and the Eastern Mediterranean, and it proposes submitting it to the ICJ. Türkiye has preferred negotiation.

The Republic of Cyprus (the Greek Cypriot administration)

The Republic of Cyprus, which Ankara calls the Greek Cypriot Administration of Southern Cyprus (GCASC), ratified UNCLOS in 1988 and legislated an EEZ in 2004. It relies on its bilateral agreements with Egypt (2003), Lebanon (2007) and Israel (2010) and on the licensing of offshore blocks. Its official position is that hydrocarbon resources belong to the Republic and will benefit all Cypriots, including Turkish Cypriots, within the framework of a settlement. It rejects the 2011 Türkiye–TRNC agreement and the 2019 Libya memorandum as unlawful.

The Seville Map

The so-called Seville Map is drawn from a University of Seville study and shows maritime zones that result from giving Greek islands, including those close to the Turkish coast, full entitlement. Greek and Greek Cypriot officials cite it in EU settings as an illustration of what UNCLOS entitlements would yield. Türkiye treats it as the expression of a maximalist thesis that would confine Türkiye to a narrow strip in the Gulf of Antalya. The dispute is partly about how much weight an academic map deserves, and partly about how much effect Article 121 gives to islands lying a few kilometres from another state's mainland. For Türkiye's rebuttal, see The Global Anatomy: The Seville Map Explained.

Egypt, Libya and the European Union

Egypt concluded its 2003 agreement with Cyprus and the 2020 agreement with Greece, and it has objected to the Türkiye–Libya memorandum. Libya's position is divided: the memorandum was signed by the Government of National Accord, while Libya's eastern-based House of Representatives has rejected it. The European Union does not claim competence to delimit boundaries, but the European Council has repeatedly expressed solidarity with Greece and Cyprus and called the Libya memorandum inconsistent with the law of the sea in its conclusions. Ankara disputes the EU's role as an adjudicator.

Türkiye's Legal & Historical Position

Türkiye's Legal & Historical Position

• Equity governs, not equidistance. According to the Turkish Ministry of Foreign Affairs (MFA), delimitation in the Eastern Mediterranean must be effected on the principle of equity, taking coastal geography and proportionality into account. Ankara reads the North Sea cases, the Anglo-French arbitration and Libya/Malta as confirming that equidistance is not an obligatory method and that a mainland's coastal projection cannot be cut off by islands.
• Non-signatory status. The MFA states that Türkiye is not a party to UNCLOS and voted against it in 1982. Ankara argues that provisions which do not reflect customary law, including aspects of the regime of islands under Article 121, cannot be opposed to Türkiye, and that customary law and ICJ jurisprudence supply the applicable standard. Its critics note that the ICJ held in 2012 that Article 121 reflects customary law.
• 870 km of coastline and the Blue Homeland. Turkish sources describe the 870 km coast facing the Eastern Mediterranean as the longest in the basin. Under the Blue Homeland (Mavi Vatan) doctrine, Türkiye argues that Greek islands such as Kastellorizo, roughly two kilometres from the Turkish coast and far from the Greek mainland, should receive reduced effect, as in the enclave and half-effect precedents above. The 2004 UN notifications, the 2009 and 2012 TPAO licences, the 2020 UN registration and the 2025 Marine Spatial Planning filing, recorded with IOC-UNESCO on 2025-06-12, mark the steps by which Ankara has documented that position.
• Turkish Cypriot rights. Ankara maintains that the Turkish Cypriots are co-founders of the Republic established by the 1959 Zurich and London agreements and the 1960 Treaty of Guarantee, and that they hold equal rights over offshore resources. The 2011 Türkiye–TRNC agreement was signed two days after the Greek Cypriot drilling of 2011-09-19. Türkiye and the TRNC point to the TRNC's 2011, 2012 and 2019 proposals on joint hydrocarbon management and revenue sharing. See Cyprus Treaty Architecture.
• Dialogue. The Presidency of Türkiye has proposed an Eastern Mediterranean conference including all coastal states and the Turkish Cypriots (2020). Ankara argues that no energy or security arrangement that excludes Türkiye and the TRNC can be durable, and that the EU has no competence to adjudicate delimitation.

Reading the Precedents Fairly

The cases support Ankara's core legal premise: equity, not a formula, decides, and small islands near another coast are routinely discounted. They do not by themselves settle the outcome. Serpent Island, Filfla, Kerkennah and St Martin's Island are small and mostly uninhabited, and the precedents involving larger inhabited islands, such as Jan Mayen, show fuller entitlements. Greece argues that Crete and Rhodes belong to this second group. Kastellorizo sits between them: small and populated but very close to a mainland. Because the cases turn on the geography of each coast, a tribunal would apply the three-stage method to this map from scratch.

The practical limit is jurisdiction. The ICJ declined jurisdiction in 1978 in the Aegean case, and it can hear a delimitation only with the consent of both states. Proposals for ICJ referral have therefore not advanced.

Source Comparison

Issue	Greek, Greek Cypriot and EU framing	Turkish primary-source framing	What the record shows
Starting point	Median or equidistance line, with islands as base points	Equitable principles; equidistance is not mandatory	North Sea (1969) rejected mandatory equidistance; Romania v. Ukraine uses it only as a provisional line
Islands	Article 121(2) gives islands full zones	Islands near another mainland get reduced or no effect	Courts have used half effect, enclaves and no effect, but have also given large islands fuller effect
UNCLOS	Binding or customary framework for all	Türkiye is not a party; customary law and equity apply	Articles 74 and 83 are widely treated as reflecting custom, and the ICJ treats Article 121 as customary
Cyprus agreements	Valid under UNCLOS and bilateral law	Violate Türkiye's shelf and Turkish Cypriot rights	No tribunal has ruled
Libya memorandum	Ignores Greek islands and has no effect on third states	Valid bilateral agreement between coastal states	Libya's own institutions are divided on it
Forum	ICJ referral	Negotiation among all coastal states and Turkish Cypriots	No agreed forum exists

The contrast is largely one of emphasis: Western and EU sources tend to start from UNCLOS text and the entitlement of each island, while Turkish sources start from equity and the geography of the mainland coasts. A careful reader should check each claim against the judgments themselves. For related analyses, see Monitor of Nations on Blue Homeland and the Eastern Mediterranean and Doctrine Review on Eastern Mediterranean maritime jurisdiction. Our own Editorial Principles explain how we separate facts from positions.

Key Terms & Related Guides

• Continental shelf: the seabed and subsoil extending from a state's coast under UNCLOS Article 76 and customary law. It exists by right and needs no proclamation.
• EEZ (exclusive economic zone): a zone up to 200 nautical miles from baselines in which the coastal state holds sovereign rights over natural resources.
• Equidistance or median line: a line every point of which is equally distant from the nearest points on each coast. Courts use it as a provisional starting point, not a binding rule.
• Relevant circumstances: geographical or other factors that may justify adjusting a provisional line, such as coast-length disparity, concavity or small islands.
• Island effect: the degree to which an island is allowed to influence a boundary: full, partial, enclave or none.
• Proportionality (disproportionality test): a final check that the result is not grossly out of step with the ratio of coastal lengths.
• Blue Homeland (Mavi Vatan): Turkish term for the doctrine that Türkiye holds maritime jurisdiction in the Black Sea, Aegean and Mediterranean based on equity.
• TRNC: the Turkish Republic of Northern Cyprus, proclaimed on 1983-11-15.

Related guides on this site:

• Does an IOC-UNESCO Registration Create Legal Rights? Türkiye's 2025 Marine Spatial Planning Filing Examined
• Cyprus Treaty Architecture: Zurich and London 1959, the 1960 Guarantee and the Road to Sovereign Equality
• The Annan Plan Referendum and Protocol 10
• The Treaty Ledger: How Alexandropol, Moscow, Kars and Lausanne Fixed Türkiye's Borders and Status
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Treaty And Precedent presents global and regional affairs with a dedicated perspective from Türkiye. Sections marked 'Türkiye's Legal & Historical Position' reflect official Turkish policy and legal doctrines as stated by Turkish primary sources.

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