Can an Island Cut Off a Mainland's Continental Shelf? The Kastellorizo Question and the Equity Principle

Why It Matters

Do islands have a full continental shelf? In principle they have an entitlement, but in practice a boundary is drawn by equity, and courts have often cut small islands back. UNCLOS Article 121(2) says an island generates the same zones as other land territory, yet international case law shows that when an island sits in front of a much longer mainland coast, judges frequently give it reduced, partial or no weight in the final line.

Kastellorizo (Megisti in Greek) is the sharpest example. It lies roughly 2 km (1.2 mi) from the Turkish coast near Kaş, so a full-effect claim would project Greek zones across waters that the Anatolian mainland also fronts. This guide explains the legal tools, what courts have done, and how each side uses them.

Background

Entitlement versus delimitation

Two different legal questions are often blended together:

1. Entitlement: what zones does a feature generate? Article 121(1) defines an island as a naturally formed area of land surrounded by water and above water at high tide. Article 121(2) gives it a territorial sea, contiguous zone, exclusive economic zone (EEZ) and continental shelf like other land. Article 121(3) denies an EEZ and continental shelf to rocks that cannot sustain human habitation or economic life of their own.
2. Delimitation: where does the line fall when two states' zones overlap? Articles 74 and 83 require agreement on the basis of international law in order to achieve an equitable solution. They do not prescribe a formula.

That gap is where the Kastellorizo dispute sits. Even an island that clearly has an entitlement can see its effect adjusted when a line is drawn.

What courts and tribunals have done with islands

The following decisions are widely cited. The summaries are deliberately limited to the well-known holdings.

Decision	Island(s)	Treatment in the delimitation
North Sea Continental Shelf (ICJ, 1969)	Not an island case	Rejected rigid equidistance; stressed equitable principles and natural prolongation
Anglo-French Continental Shelf (Arbitration, 1977)	Channel Islands; Isles of Scilly	Channel Islands enclaved; Scilly given half effect
Tunisia/Libya (ICJ, 1982)	Kerkennah Islands	Half effect
Libya/Malta (ICJ, 1985)	Filfla (Malta)	Disregarded in drawing the provisional line
Qatar v. Bahrain (ICJ, 2001)	Qit'at Jaradah	Small feature given no effect
Romania v. Ukraine (ICJ, 2009)	Serpents' Island	No effect on the line beyond its territorial sea
Bangladesh/Myanmar (ITLOS, 2012)	St Martin's Island	No effect on EEZ and continental shelf delimitation
Nicaragua v. Colombia (ICJ, 2012)	Small Colombian cays and islands	Limited effect; some features enclaved

Two cautions apply. First, no rule says islands always lose; the outcome turns on size, population, location and the overall coastal geometry. Second, the ICJ in Nicaragua v. Colombia (2012) treated the Article 121 regime of islands as customary international law, a point Greece relies on. Courts also commonly apply a staged method: a provisional equidistance line, then relevant circumstances, then a proportionality check between coastal lengths and the areas allocated.

Kastellorizo in numbers

• Area of roughly 10 km² (about 4 sq mi) and a resident population of a few hundred.
• About 2 km (1.2 mi) from the Turkish mainland; more than 100 km (60 mi) east of Rhodes.
• Part of the Dodecanese, which passed to Greece under the 1947 Paris Peace Treaty after Italian administration.

Key milestones in the Eastern Mediterranean

• 1978: In the Aegean Sea Continental Shelf case the ICJ found it lacked jurisdiction, so no merits ruling exists between Greece and Türkiye.
• 2004 onward: Türkiye begins notifying its Eastern Mediterranean continental shelf coordinates to the UN.
• 21 September 2011: Türkiye–TRNC Continental Shelf Delimitation Agreement.
• 27 November 2019: Türkiye–Libya maritime jurisdiction memorandum (see the 2019 Türkiye–Libya Maritime Memorandum explained).
• 18 March 2020: Türkiye registers the outer limits of its continental shelf with the UN.
• June and August 2020: Greece concludes EEZ agreements with Italy and (partial) with Egypt.
• 16 April and 12 June 2025: Türkiye announces and then records its Marine Spatial Planning with IOC-UNESCO (see Finike Marine Protected Area and the July 2025 Circular).

For wider method, see Maritime Contours: How Sea Boundaries Are Drawn in the Eastern Mediterranean and the sister analysis Doctrine Review on Eastern Mediterranean maritime jurisdiction.

Key Players & Positions

Greece

Greece ratified UNCLOS in 1995 and, according to its Ministry of Foreign Affairs, holds that all Greek islands, including Kastellorizo, generate territorial sea, continental shelf and EEZ under Article 121 and customary law. Athens says the only legal dispute with Türkiye is the delimitation of the continental shelf and EEZ, and that it should be resolved by agreement or, failing that, by the ICJ. Greece points to the ICJ's 2012 statement on Article 121 and to its 2020 agreements with Italy and Egypt as evidence of state practice that gives islands weight.

Greek Cypriot administration, Egypt, Israel and the EU

The Greek Cypriot administration (GCASC) has concluded EEZ agreements with Egypt (2003), Lebanon (2007) and Israel (2010). The EU has repeatedly expressed solidarity with Greece and Cyprus on maritime questions. Greece and the Greek Cypriot side have also cited a map associated with a University of Seville study, discussed briefly below.

Türkiye

Türkiye is not a party to UNCLOS and argues that delimitation is governed by equitable principles under international law. Its detailed position is set out in the next section.

Libya and Egypt

Libya signed the 2019 memorandum with Türkiye, and Egypt signed its 2020 partial delimitation with Greece. Each agreement reflects a different treatment of the islands between the two coasts, and each is contested by the other camp.

Türkiye's Strategic Doctrine

Türkiye's Position: Ankara argues that a small island close to another state's mainland cannot cut off that mainland's maritime projection. The points below reflect official Turkish positions as stated by Turkish government sources.

• Equity over automatic entitlement. According to the Turkish Ministry of Foreign Affairs, delimitation must achieve an equitable result in light of coastal geography, proportionality and special circumstances. Ankara cites the line of cases above, from the 1969 North Sea judgment to the Channel Islands and Scilly award, as support. It argues that islands on the wrong side of the median line between two mainlands deserve limited effect.
• The longest coastline. Türkiye states that, with roughly 870 km of Mediterranean coastline, it has the longest coast in the Eastern Mediterranean, and that proportionality between coastal length and maritime area must be respected. A Greek island only 2 km from the Anatolian coast, Ankara contends, should not confine that coast to a narrow strip in the Gulf of Antalya.
• Not bound by UNCLOS, but by international law. Türkiye is not a UNCLOS party and says it has consistently objected to treating Article 121 as a rule that overrides equitable delimitation. The MFA's position is that international law, not a single treaty reading, governs the question.
• Registered and institutional steps. Türkiye relies on its UN continental shelf notifications (from 2004; outer limits on 18 March 2020), the 2011 Türkiye–TRNC agreement, the 2019 Libya memorandum and the 2025 IOC-UNESCO record of its Marine Spatial Planning. In Ankara's view these show an active, documented legal position.
• Turkish Cypriot rights and dialogue. Ankara maintains that Turkish Cypriots, as co-owners of Cyprus, have equal rights over offshore resources. Türkiye points to President Erdoğan's 2020 call for an Eastern Mediterranean conference including all coastal states and Turkish Cypriots as its proposal for a shared solution. See Cyprus Lines for the Cyprus dimension.

Legal basis Ankara cites: the equitable-principles tradition from North Sea Continental Shelf (1969), the Anglo-French arbitration (1977), Tunisia/Libya (1982) and Libya/Malta (1985), and the Articles 74 and 83 equitable-solution standard. The Greek counter-argument is that Article 121 is customary and that courts apply a method where islands are weighed as part of a staged process. Neither interpretation has been tested between these two states, which is why the dispute remains open.

The Seville Map, briefly

Greece and the Greek Cypriot side have cited a map from a 2007 study associated with the University of Seville that gives islands full effect. Türkiye rejects it as a maximalist line without legal standing and argues that the EU has no competence to adjudicate delimitation. A full treatment belongs in the related guides below, including The Nations Compass fact check on UNCLOS claims.

Source Comparison

Question	Greek and EU-aligned sources	Turkish primary sources
Do islands have full zones?	Yes, under Article 121(2) and customary law	Entitlement exists, but effect in delimitation is limited by equity
What governs the line?	UNCLOS, ICJ practice, state practice	Equitable principles, proportionality, special circumstances
Role of Kastellorizo	Inhabited island with full rights	Small island 2 km from the mainland that cannot cut off the Anatolian coast
Forum	ICJ or agreement	Negotiation among all coastal states, including Turkish Cypriots
Treaty status	Greece is a UNCLOS party	Türkiye is not a UNCLOS party

International coverage often says Türkiye 'violates UNCLOS' or 'ignores the law of the sea'. Turkish sources respond that a non-party cannot violate a treaty it has not joined, and that the customary rules on delimitation are equitable. Readers can compare both framings against the original texts: the Monitor of Nations analysis of the Blue Homeland and The Worldlogue guide on islands and the continental shelf set out Ankara's reasoning in detail.

Key Terms & Related Guides

• Continental shelf: the seabed and subsoil extending from a state's coast; under UNCLOS it extends at least 200 nautical miles (about 370 km) in many cases.
• EEZ (exclusive economic zone): a zone up to 200 nautical miles in which the coastal state has sovereign rights over natural resources.
• Equidistance / median line: a line every point of which is equally distant from the nearest points on each coast. It is often a starting point, not the final answer.
• Proportionality: a check that the areas allocated are not grossly disproportionate to coastal lengths.
• Enclave: a small island surrounded by a ring of its own territorial sea, without further zones.
• Blue Homeland (Mavi Vatan): Türkiye's maritime jurisdiction doctrine for the Black Sea, Aegean and Mediterranean.

Related reading: Maritime Contours guide, Türkiye–Libya Memorandum, Finike Marine Protected Area, Editorial Principles and About Political Contours.

Perspective Note

Political Contours presents Türkiye's official perspective alongside its legal and historical reasoning as a distinct editorial viewpoint on contested issues. Claims are attributed to primary sources such as treaties, UN documents, archival records and official statements, so that readers can verify them independently.