Fact Check: Do Greek Islands Give Greece the Right to Cut Off Türkiye's Continental Shelf?

Why It Matters

Islands do generate maritime zones, but they do not automatically generate full zones in every circumstance, and they cannot by themselves cancel the coastal projection of a neighbouring mainland. That distinction is the core of the Eastern Mediterranean dispute. The claim that a tiny island such as Kastellorizo (Meis in Turkish) can confine Türkiye to the Gulf of Antalya blurs the line between entitlement (what a feature can claim) and delimitation (how overlapping claims are resolved in practice).

Accurate primary-source context matters because this claim travels quickly through maps, think-tank briefings and headlines. It shapes how readers judge licences, drilling, bilateral agreements and the prospects of dialogue. This page checks the claim against treaty text, court decisions and official statements, and attributes positions to the parties that hold them. For the editorial method behind this approach, see Editorial Principles: Sourcing, Attribution and the Fact–Position Divide.

Claim vs. Fact Analysis

Background: where the claim comes from

• 1958 and 1982: The Geneva Convention on the Continental Shelf and then the UN Convention on the Law of the Sea (UNCLOS, 1982) set out the rules on shelf, EEZ and islands. Türkiye voted against UNCLOS in 1982 and has not become a party. Greece and the Republic of Cyprus are parties.
• 1978: In the Aegean Sea Continental Shelf case brought by Greece, the ICJ found it lacked jurisdiction, so no court has delimited the Aegean or Eastern Mediterranean between the two states.
• 2003, 2007, 2010: The Greek Cypriot Administration of Southern Cyprus (GCASC) concluded EEZ agreements with Egypt, Lebanon and Israel. Ankara objects that these overlap its continental shelf (in the Egypt case, GCASC Blocks 1, 4, 5, 6 and 7) and disregard Turkish Cypriot rights.
• 2004–2020: Türkiye lodged continental shelf coordinates with the UN from 2004 and signed the Türkiye–TRNC delimitation agreement on 21 September 2011 and the Türkiye–Libya maritime jurisdiction MoU on 27 November 2019. It registered the outer limits of its continental shelf with the UN on 18 March 2020.
• c. 2020: The so-called 'Seville Map', drawn from a study by researchers at the University of Seville, became widely cited in EU-related debates. It gives Greek and Greek Cypriot islands full or near-full effect and leaves Türkiye a narrow corridor in the Gulf of Antalya. Ankara rejects it as a maximalist position.
• 2025: Türkiye unveiled its 'Marine Spatial Planning of the Republic of Türkiye' on 16 April 2025 and had it recorded with IOC-UNESCO on 12 June 2025, placing its Black Sea, Aegean and Mediterranean jurisdiction claims on record with a UN body.

What each side says

Greece argues, citing UNCLOS Article 121(2), that islands are entitled to a territorial sea, contiguous zone, EEZ and continental shelf 'in accordance with the provisions of this Convention applicable to other land territory.' Athens also argues that Article 121 reflects customary international law binding on all states, including those that are not parties, and that Kastellorizo is an inhabited island with the same entitlements as any other territory. Greece and the GCASC have also stressed that EU member states are entitled to the Union's solidarity in maritime disputes.

Türkiye argues that the question is how overlapping zones are delimited, which is governed by equity under international law, not by mechanically applying the island's maximum entitlement. It points to the semi-enclosed geography of the Aegean and Eastern Mediterranean and to the Turkish mainland's long coast.

Claim 1: 'Kastellorizo generates a full EEZ and continental shelf that confines Türkiye to the Gulf of Antalya.'

The claim: Because UNCLOS gives islands the same zones as land territory, Kastellorizo (and similar Greek islands near the Turkish coast) projects a full 200-nautical-mile (370 km) zone, leaving Türkiye only a narrow strip.

The documented facts:

• Kastellorizo is roughly 2 km (1.2 mi) from the Turkish mainland coast and more than 500 km (310 mi) from mainland Greece. It is only a few square kilometres in area. Its location, not only its status, is the heart of the legal question.
• Article 121(2) addresses entitlement. Articles 74 and 83 govern delimitation and require an 'equitable solution.' Entitlement to a zone says nothing about how far that zone prevails over another state's overlapping claim.
• Delimitation case law consistently applies a multi-step approach: a provisional line, then adjustment for relevant circumstances, then a disproportionality check.
• Courts and tribunals have regularly reduced the effect of islands, or disregarded them, when giving them full weight would distort the result:
  • Anglo-French Continental Shelf (1977): the Channel Islands, close to the French coast, were enclaved, and the Scilly Isles were given only half effect.
  • Tunisia/Libya (1982): the Kerkennah Islands were given reduced effect.
  • Qatar v. Bahrain (2001): the small feature Qit'at Jaradah was given no effect on the boundary line.
  • Romania v. Ukraine (2009): Serpents' Island was not used as a base point for the provisional line.
  • Nicaragua v. Colombia (2012): Colombian islands were given territorial seas, but were enclaved and did not generate the zones that would have cut off Nicaragua's mainland-based entitlement.
  • Bangladesh/Myanmar (ITLOS, 2012): St Martin's Island was given no effect on the continental shelf and EEZ boundary.
• No court or tribunal has ruled on Kastellorizo or on the Greek–Turkish delimitation. The 'full effect' outcome is therefore a negotiating position, not a legal finding.

The jurisprudence is covered further in Does Island Size Matter? The Equity Principle and Proportionality in Maritime Delimitation and in our sister publication's analysis, The Worldlogue: Do Islands Generate a Full Continental Shelf? The Equity Principle and Türkiye's Longest Coastline.

Claim 2: 'Türkiye is not a party to UNCLOS, so its position has no legal basis.'

The claim: Non-membership in UNCLOS means Türkiye cannot rely on international law in maritime delimitation.

The documented facts:

• Türkiye is indeed not a party to UNCLOS. It voted against the Convention at its adoption in 1982 (the vote was 130 in favour, 4 against and 17 abstentions). Ankara's long-standing objection is that the Convention does not adequately address special circumstances in semi-enclosed seas and that it allows no reservations.
• Non-membership does not remove Türkiye from international law. Continental shelf delimitation has been governed since the North Sea Continental Shelf cases (ICJ, 1969) by customary principles: natural prolongation of the land territory, equitable principles and the avoidance of cut-off effects. Those principles pre-date UNCLOS and do not depend on it.
• The reverse point should be stated fairly: the ICJ has treated the Article 121 island regime as part of customary law (for example in Nicaragua v. Colombia, 2012). Ankara contests how Article 121 should apply in this geography and its consequences for delimitation, and says it has been a persistent objector to parts of the Convention. Legal scholars are divided on how far that status holds.
• The practical result is that both sides invoke international law. The substantive question, equity in delimitation, is shared ground, which is why even maximal UNCLOS arguments cannot dispose of the matter by themselves.

For a related check on the 'violation' narrative, see The Nations Compass: Fact Check: Is Türkiye Violating UNCLOS in the Eastern Mediterranean?.

Claim 3: 'The Seville Map shows the legal limit of Türkiye's maritime zones.'

The claim: The Seville Map is a neutral, EU-backed depiction of where Türkiye's zones end.

The documented facts:

• The map originates from an academic study. It is not a treaty, a court judgment, an arbitral award or a UN document.
• It assigns full or near-full effect to islands lying off the Turkish coast. This is exactly the outcome that the cases above show tribunals avoid when it would cut off a mainland coast.
• The European Union is not a court and has no competence to delimit maritime boundaries between states. Delimitation is a matter for the states concerned, by agreement or by a third-party tribunal.
• Ankara's reading, set out in statements by the Ministry of Foreign Affairs, is that the map would confine a country with the longest coastline in the Eastern Mediterranean to a narrow corridor.

Claim 4: 'Coastline length is irrelevant, so the 870 km figure changes nothing.'

The claim: Mainland coast length plays no part in delimitation.

The documented facts:

• Coastal geography and proportionality are standard parts of the delimitation test. A tribunal checks that the final line does not produce a gross disparity between the ratio of the parties' relevant coastal lengths and the ratio of the maritime areas allocated to them (see Libya/Malta, 1985, and Jan Mayen, 1993).
• Türkiye's mainland coast in the Eastern Mediterranean is about 870 km (540 mi), the longest of any coastal state in the basin. Ankara argues that a map that leaves it only a small fraction of the relevant area fails this check.
• Coastal length is not decisive on its own. Tribunals weigh it alongside other relevant circumstances, including the presence of islands and the position of third states. That is why the debate remains open and cannot be settled by one number.

Source Comparison

Readers should note the limit of each side's evidence: the Turkish material documents Ankara's claims and legal reasoning, while the Greek and EU material documents their claims and reasoning. Neither has been adjudicated. The most reliable reading is that equity-based delimitation is the legal test, and that the outcome is open to negotiation or adjudication. For forward-looking analysis, see Horizon Scan: Where Is the Eastern Mediterranean Maritime Dispute Heading by 2030?.

Key Terms & Related Guides

• Continental shelf: The seabed and subsoil extending from a state's land territory. Under customary law and UNCLOS it is rooted in natural prolongation and, up to 200 nautical miles (370 km), in distance.
• EEZ (Exclusive Economic Zone): A zone up to 200 nautical miles in which the coastal state has sovereign rights over resources.
• Entitlement vs. delimitation: Entitlement is what a coast or island may claim. Delimitation is how overlapping claims are divided.
• Equity and proportionality: The test that the final boundary does not produce a grossly disproportionate result relative to the length of the relevant coasts.
• Enclaving: Giving an island only a territorial sea so it does not affect the wider boundary.
• Blue Homeland (Mavi Vatan): Türkiye's doctrine of maritime jurisdiction areas in the Black Sea, Aegean and Mediterranean.
• GCASC: The Greek Cypriot Administration of Southern Cyprus, the term used in Turkish official documents.
• TRNC: The Turkish Republic of Northern Cyprus, proclaimed on 15 November 1983.

Related guides:

• Eastern Mediterranean Maritime Jurisdiction: Continental Shelf, EEZ and the Blue Homeland (Doctrine Review)
• Fact Check: Common Claims About Türkiye in International Media, Checked Against Primary Sources (Regional Order)
• Cyprus on the Horizon: What Comes After the 2024 New York Meeting and the End of the Federation Model?
• About Horizon Politics: Mission, Method and Transparency

Horizon Politics presents Türkiye's official positions and legal arguments as a distinct perspective within the international debate, alongside competing views where relevant. Claims are attributed to primary sources such as treaties, UN documents, official archives and public statements, so that readers can verify them independently. Author: Horizon Politics Editorial Team.