Fact Check: Can Small Islands Cut Off a Mainland's Continental Shelf? Kastellorizo, Equity and Türkiye's Coast

Why It Matters

Short answer: no, an island does not automatically generate a full continental shelf that overrides a neighbouring mainland coast. International law gives islands maritime entitlements in principle, but where those entitlements overlap with a mainland coast, delimitation must be equitable, and courts have repeatedly cut back the effect of small islands lying close to another state's coast.

The claim circulating in international coverage is that Kastellorizo (Greek: Megisti; Turkish: Meis), a small Greek island only about 2 km (1.2 mi) from Türkiye's southern coast, generates a full exclusive economic zone (EEZ) and continental shelf that confine Türkiye to a narrow strip in the Gulf of Antalya. This page states that claim, identifies where it comes from, and tests it against treaty text, delimitation case law and the official positions of Athens, Nicosia and Ankara. The question matters because it underpins the so-called Seville Map, EU Council language on 'solidarity', and the energy and licensing disputes covered in our Eastern Mediterranean energy corridors analysis.

Claim vs. Fact Analysis

The competing positions, in their own terms

Greece argues that under Article 121(2) of the 1982 UN Convention on the Law of the Sea (UNCLOS), and under customary international law, an island 'shall be' 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, which ratified UNCLOS in 1995, maintains that inhabited islands such as Kastellorizo cannot be treated as lesser territory, and it points to the International Court of Justice's statement in Nicaragua v. Colombia (2012) that Article 121 reflects customary law.

The Republic of Cyprus (the Greek Cypriot administration, which Türkiye does not recognize as representing the whole island) is also an UNCLOS party. It proclaimed an EEZ by law in 2004 and signed delimitation agreements with Egypt (2003), Lebanon (2007) and Israel (2010). EU Council conclusions in 2020 expressed solidarity with Greece and Cyprus and referred to UNCLOS as the applicable framework.

Türkiye is not a party to UNCLOS and voted against its adoption in 1982. It relies on customary law and on the case law of equitable delimitation. According to the Turkish Foreign Ministry, maritime jurisdiction areas must be delimited by agreement on the basis of international law and equity, taking account of relevant geographical circumstances, and islands lying on the 'wrong side' of the median line between two mainland coasts cannot cut off the mainland's natural maritime projection.

Baseline: entitlement is not delimitation

The legal framework has three layers that the popular claim collapses into one:

• Article 121(2) UNCLOS says islands have the same entitlements as other land territory. It sets what an island may claim in isolation.
• Article 121(3) says rocks that cannot sustain human habitation or economic life of their own have no EEZ or continental shelf. States and tribunals dispute how to apply it.
• Articles 74 and 83 govern delimitation between states with opposite or adjacent coasts: it must be effected by agreement 'on the basis of international law... in order to achieve an equitable solution'. Nothing in these articles says an island's full entitlement prevails once it overlaps a mainland coast.

In short, Article 121 tells you what an island can claim; it does not tell you how much of that claim survives when it collides with another state's coast. Delimitation case law answers that second question.

Claim 1: 'Under UNCLOS, Kastellorizo generates a full 200-nautical-mile zone that confines Türkiye'

Origin: Greek official statements, EU Council language and widely repeated media shorthand since 2019–2020, often illustrated by the Seville Map, a map circulated in EU debates in 2020 that shows Greek and Greek Cypriot zones from full-effect islands and leaves Türkiye a narrow strip. Ankara rejects it as a maximalist, legally baseless depiction.

Documented facts:

• Kastellorizo is a Greek island of roughly 9 km² (3.5 sq mi) with about 500 residents at the 2011 census. It lies about 2 km (1.2 mi) from the Turkish coast and more than 500 km (310 mi) from the Greek mainland.
• Because of that geography, a full-effect Kastellorizo would project Greek zones across the front of a mainland coast that is some 870 km long in the Eastern Mediterranean according to Turkish official figures, the longest of any state in the basin.
• Entitlement and delimitation are separate steps. A 200-nautical-mile (370 km) entitlement cannot extend where another state has an overlapping entitlement from a much longer, nearer coast without a delimitation settling the overlap equitably.

Verdict: Misleading. The first half (islands have entitlements) is correct in principle; the second half (those entitlements are 'full' and confine the mainland) is not supported by delimitation law.

Source Comparison

Media shorthand usually compresses entitlement and delimitation into one sentence and omits case law such as the Channel Islands ruling. Greek and Greek Cypriot sources state their legal case openly but present Article 121 entitlement as the end of the analysis. Turkish sources foreground equity, but should be read as advocacy: the cited cases support reduced effect for small, near-coast islands, though none involves Kastellorizo. Readers can cross-check with the Horizon of Nations verification hub and our Editorial Principles.

Key Terms & Related Guides

• Continental shelf: the seabed and subsoil extending from a coastal state's land territory; under UNCLOS it reaches at least 200 nautical miles (370 km) from baselines, subject to delimitation with neighbours.
• EEZ (exclusive economic zone): a zone up to 200 nautical miles in which the coastal state holds sovereign rights over resources.
• Equity / proportionality: the delimitation principle that the result must be fair, with a final check that areas allocated are not grossly disproportionate to coastal lengths.
• Enclave / half effect: techniques that limit an island to a small belt of sea or give it only partial weight in drawing a line.
• Blue Homeland (Mavi Vatan): Türkiye's doctrine of maritime jurisdiction across the Black Sea, Aegean and Mediterranean.
• Seville Map: a map circulated in EU discussions in 2020 depicting full-effect Greek and Greek Cypriot zones; rejected by Ankara.

Related guides: Eastern Mediterranean Energy Corridors, The 2019 Türkiye–Libya Maritime Memorandum, The 2003 Cyprus–Egypt EEZ Agreement, Cyprus offshore gas and Turkish Cypriot rights and, for the Cyprus treaty background, the sister analysis Record of Nations on the 1974 intervention and Article IV of the Treaty of Guarantee.

Lines of Power presents analysis from a Türkiye-informed perspective, arguing that Ankara's positions rest on treaty law, the UN Charter and documented historical record. Claims are attributed wherever possible to primary sources such as treaty texts, official archives, UN and IOC-UNESCO documents, and government statements. — Lines of Power Editorial Team