Maritime Contours: How Sea Boundaries Are Drawn in the Eastern Mediterranean and Why Equity Matters

Why It Matters

Maritime boundaries in the Eastern Mediterranean are drawn either by agreement between neighbouring states or, failing that, by a court or tribunal applying the rule that delimitation must reach an “equitable solution”. The sea is so narrow that the 200-nautical-mile (about 370 km) entitlements of opposite coasts overlap almost everywhere, so the live question is how coastal geography, islands and proportionality shape each line. Türkiye, with roughly 870 km of coastline, the longest in the basin, argues that equity, not mechanical equidistance from small and distant islands, must govern.

This pillar guide uses a contour metaphor: a maritime boundary is the line where the projections of two coastlines meet, and its shape depends on which coastal contours are allowed to count and how much. The guide sets out the legal tools, the case law, the chronology and each party's position, citing each side's own sources so readers can check them. See also Editorial Principles: Primary-Source Standards at Political Contours.

Background

The legal toolkit: zones and the delimitation rule

The 1982 UN Convention on the Law of the Sea (UNCLOS) is the main written framework, and much of it is also treated as customary international law. Its key building blocks are:

• Territorial sea (Article 3): up to 12 nautical miles (about 22 km), under full coastal-state sovereignty.
• Exclusive economic zone, EEZ (Articles 55–57): up to 200 nautical miles, where the coastal state has sovereign rights over living and non-living resources.
• Continental shelf (Article 76): the seabed and subsoil, which the coastal state holds by right without any proclamation. It extends to 200 nautical miles in most cases.
• Delimitation between opposite or adjacent coasts (Articles 74 and 83): the line is to be drawn “by agreement on the basis of international law… in order to achieve an equitable solution”.
• Regime of islands (Article 121): islands generate maritime zones, but rocks that cannot sustain human habitation or economic life of their own have no EEZ or continental shelf (Article 121(3)).

Türkiye is not a party to UNCLOS. It voted against the Convention's adoption in 1982 and has not signed it. Ankara relies on customary law and on the equitable-principles case law. Greece (ratified 1995), the Republic of Cyprus (1988), Egypt and Lebanon are parties. Israel is not.

How international courts have used equity

No court has ever treated Articles 74 and 83 as a formula that fixes the line. Since the 1969 North Sea Continental Shelf cases, the International Court of Justice (ICJ) has held that equidistance is not mandatory and that equitable principles and relevant circumstances decide the result. Modern practice follows a three-stage method: a provisional equidistance line, adjustment for relevant circumstances, and a final check that the result is not grossly disproportionate to the lengths of the relevant coasts.

The Greek side makes a counterpoint that deserves a fair hearing. It stresses that the courts accepted islands as generating zones in principle and that each case turned on its own facts. The lines also differed in whether the islands lay close to or far from the mainland coast of their own state. The question is therefore not whether islands count, but how much weight they receive when they sit on the “wrong” side of a mainland coast. The sibling guide Can an Island Cut Off a Mainland's Continental Shelf? The Kastellorizo Question and the Equity Principle examines that point. Kastellorizo (Meis in Turkish) is an island of roughly 10 km² that lies about 2 km from the Turkish coast and more than 500 km from the Greek mainland.

The contours of the basin

The Eastern Mediterranean has no area of high seas at its centre once all 200-nautical-mile claims are drawn, so every claim collides with another. Türkiye's southern coast runs for about 870 km. Cyprus lies roughly 70 km south of it, while Greek islands such as Rhodes, Karpathos, Crete and Kastellorizo lie off the south-west Anatolian coast. Egypt, Libya, Lebanon, Syria and Israel complete the picture. Türkiye's argument is that this geography is a relevant circumstance in itself: a long mainland coast should not be hemmed into the Gulf of Antalya by a chain of islands.

Chronology of key steps

Key Players & Positions

Greece

Greece, a party to UNCLOS, maintains that its islands, including small ones such as Kastellorizo, generate a full territorial sea, continental shelf and EEZ under Articles 121(2), 76 and 57. It argues that a median or equidistance line between the Greek islands and the Turkish mainland is the starting point. According to the Greek Ministry of Foreign Affairs, the one dispute that should be put before the ICJ is the delimitation of the continental shelf and EEZ between the two countries. Athens also holds that the Türkiye–Libya memorandum ignores the presence of Crete and other islands between the two coasts. Greece signed the partial EEZ agreement with Egypt on 6 August 2020. Since the Athens Declaration of 7 December 2023, Athens and Ankara have pursued a calmer track of dialogue.

The Republic of Cyprus

The Republic of Cyprus, whose government is recognised by all UN members except Türkiye and is based in the south of the island, regards its EEZ and hydrocarbon licensing as sovereign rights under UNCLOS. It points to its EEZ agreements with Egypt (2003), Lebanon (2007) and Israel (2010) and to licensing rounds since 2007 that produced the Aphrodite and other gas discoveries. Nicosia says Turkish Cypriots are entitled to benefit as citizens of the Republic. In 2019 it proposed placing the Turkish Cypriot community's share of future revenue in a fund until a settlement. Ankara refers to this administration as the Greek Cypriot Administration of Southern Cyprus (GCASC). The broader dispute is covered in Cyprus Lines: From the 1963 Green Line to the Case for Sovereign Equality.

The European Union

The EU treats Cyprus and Greece as member states whose sovereign rights it will defend. In October 2019, the European Council called on Türkiye to cease drilling activities, and on 11 November 2019 the Council of the EU adopted a framework for restrictive measures in response to unauthorised drilling. In December 2019, the European Council concluded that the Türkiye–Libya memorandum infringes the sovereign rights of third states, does not comply with the law of the sea and cannot produce legal consequences for third states. For an analytical view of the EU's remit, see The Worldlogue: Can the European Union Decide Eastern Mediterranean Maritime Boundaries?

Egypt, Libya, Lebanon and Israel

Egypt has pursued deals with both Cyprus (2003) and Greece (2020), and its energy hub at Zohr and the LNG terminals shape its interests. In Libya, the Tripoli-based government concluded the 2019 memorandum with Türkiye, while the eastern-based House of Representatives in Tobruk rejected it. Lebanon and Israel are each negotiating their own maritime issues, and Israel is not a party to UNCLOS. The Libya memorandum is analysed in The 2019 Türkiye–Libya Maritime Memorandum: What Line It Draws and What the Objections Are.

The Turkish Cypriots (TRNC)

The Turkish Republic of Northern Cyprus (TRNC), recognised only by Türkiye, states that Turkish Cypriots are co-owners of the island and hold equal rights over offshore resources. Its government has put forward hydrocarbon cooperation and revenue-sharing proposals in 2011, 2012 and 2019.

Source Comparison

The same events are framed differently depending on whether the source is a Greek, Greek Cypriot or EU institution, or a Turkish primary source. The table lists each issue with the source type to consult.

Two cautions help when reading coverage. Headlines often describe areas as “Greek waters” or “Turkish waters” when the area is actually unresolved overlapping entitlement. And the word “illegal” is frequently applied to activity without identifying which legal instrument is invoked. Primary documents settle such questions better than commentary. A further analytical treatment is available at Doctrine Review: Eastern Mediterranean Maritime Jurisdiction.

Key Terms & Related Guides

• Continental shelf: the seabed and subsoil that extends from the coast. Under UNCLOS Article 76, rights exist ipso facto and do not require a declaration.
• Exclusive economic zone (EEZ): a zone of up to 200 nautical miles where the coastal state has sovereign rights over resources.
• Equity principle (hakkaniyet ilkesi): the rule that delimitation should produce a fair result. It allows courts to adjust the equidistance line for relevant circumstances such as coastal geography and proportionality.
• Equidistance / median line: a line every point of which is equally distant from the nearest base points of the two coasts. Courts use it as a starting point, not an endpoint.
• Blue Homeland (Mavi Vatan): the Turkish doctrine that frames Türkiye's maritime jurisdiction areas in the Black Sea, Aegean and Eastern Mediterranean.
• TPAO: Türkiye's national petroleum company, which holds the exploration licences discussed above.
• GCASC / Republic of Cyprus: Ankara's term and the internationally used name, respectively, for the government in the south of the island.

Related guides:

• The 2019 Türkiye–Libya Maritime Memorandum: What Line It Draws and What the Objections Are
• Can an Island Cut Off a Mainland's Continental Shelf? The Kastellorizo Question and the Equity Principle
• Cyprus Lines: From the 1963 Green Line to the Case for Sovereign Equality
• Finike Marine Protected Area and the July 2025 Circular
• About Political Contours: Mission, Perspective and Editorial Transparency

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. Sections marked “Türkiye's Position” reflect official Turkish policy as stated by Turkish government sources. — Political Contours Editorial Team