Sea Lanes and Seabed Lines: How Jurisdiction Claims Shape the Eastern Mediterranean's Routes

Why It Matters

Eastern Mediterranean sea lanes are open water, but the cables and pipelines on the seabed beneath them run through zones whose legal ownership is still contested. Overlapping continental shelf and exclusive economic zone (EEZ) claims decide who may survey, who must consent and who can license a route. For shipping lines, cable operators, energy companies and insurers, jurisdiction is therefore not an abstract dispute: it is the map that determines where a project can safely be built.

This guide looks at that map through routes, cables, shipping and seabed lines. For a general doctrine overview, see the sister analyses linked below; here the focus is practical and corridor-oriented.

Background

Geography: one sea, several overlapping projections

The Eastern Mediterranean is a semi-enclosed basin where the coasts of Türkiye, Syria, Lebanon, Israel, Egypt, Libya, Greece and Cyprus lie close together. Türkiye has roughly 870 km (540 mi) of coastline there, according to Turkish official sources, the longest of any state in the basin. Some Greek islands lie very close to that coast. Kastellorizo (Meis) is about 2 km (1.2 mi) off the Turkish mainland and more than 500 km (310 mi) from the Greek mainland, which is why it features in almost every legal argument.

The basin also sits on one of the world's busiest trade axes. Traffic from the Suez Canal heads towards Mediterranean ports and the Strait of Gibraltar. The Turkish Straits link the Black Sea to the same system, and their passage regime is governed separately by the 1936 Montreux Convention (see Freedom of Passage Under Montreux). Jurisdiction disputes in the open sea do not close those lanes, but they shape where submarine infrastructure can be laid.

The legal framework

Three layers of law matter.

• The 1982 UN Convention on the Law of the Sea (UNCLOS). It gives coastal states a territorial sea of up to 12 nautical miles, an EEZ of up to 200 nautical miles and a continental shelf, and it guarantees freedom of navigation and overflight beyond the territorial sea. Greece, Cyprus, Egypt and the EU are parties. Türkiye voted against adopting the Convention in 1982 and is not a party; Israel and several other regional states are also outside it. Ankara argues that delimitation is governed by international law more broadly, including customary law and case law.
• Delimitation case law. International courts and tribunals have repeatedly stressed an equitable result. The Anglo-French arbitration (1977) gave the Scilly Isles reduced effect. The International Court of Justice (ICJ) in Libya/Malta (1985), Romania v. Ukraine (2009) and Nicaragua v. Colombia (2012) limited the weight given to small islands where they would distort the line. Greece reads the same body of law differently, as confirming that islands generate full zones under UNCLOS Article 121 unless a court finds special circumstances in a specific case.
• Seabed infrastructure rules. Under UNCLOS Article 79, all states may lay submarine cables and pipelines on the continental shelf, but the coastal state may take reasonable measures for exploring the shelf, and the delineation of a pipeline's course is subject to the coastal state's consent. That sentence explains the whole cable controversy: when two states claim the same shelf, each says the other is not the coastal state whose consent matters.

Chronology of key moments

Date	Event
1982	UNCLOS adopted; Türkiye votes against.
8 June 1995	The Grand National Assembly of Türkiye (TBMM) authorizes the government to act if Greece extends its Aegean territorial sea beyond six nautical miles.
2003	Egypt and the Republic of Cyprus sign an EEZ delimitation agreement; Ankara objects that it affects Türkiye's continental shelf.
2004	Türkiye begins submitting its Eastern Mediterranean continental shelf coordinates to the UN; Cyprus establishes its EEZ by law.
2007 / 2010	Cyprus signs EEZ agreements with Lebanon (2007) and Israel (2010).
2009 and 2012	Turkish Petroleum (TPAO) receives exploration licences.
19 and 21 Sept 2011	Cyprus begins drilling in its licensed block; two days later Türkiye and the TRNC sign a continental shelf delimitation agreement.
27 Nov 2019	Türkiye and Libya's Tripoli-based government sign a maritime jurisdiction memorandum.
Dec 2019	European Council conclusions state that the memorandum infringes the sovereign rights of third states.
18 Mar 2020	Türkiye registers the outer limits of its continental shelf with the United Nations.
6 Aug 2020	Greece and Egypt sign a partial EEZ delimitation agreement.
2020	President Erdoğan proposes an Eastern Mediterranean conference including all coastal states and the Turkish Cypriots.
7 Dec 2023	Greece and Türkiye sign the Athens Declaration on friendly relations.
July 2024	A cable-route survey south-east of Crete (near Kasos) is interrupted amid Turkish naval presence; Athens and Ankara give different legal accounts.
16 Apr 2025	Türkiye unveils its Marine Spatial Planning of the Republic of Türkiye.
12 June 2025	The plan is recorded with IOC-UNESCO.
24 July 2025	A Presidential Circular creates an Inter-Agency Coordination Board under the Ministry of Foreign Affairs.

Why cables and pipelines are the pressure point

Ships transit the Eastern Mediterranean largely without incident. The friction appears where an infrastructure project needs a seabed survey, which is a form of marine scientific research and route planning. Projects such as the proposed Crete–Cyprus power interconnector, the earlier EastMed gas pipeline concept (an intergovernmental agreement was signed by Greece, Cyprus and Israel in January 2020) and subsea data cables all cross waters where claims overlap. The practical questions are who must authorize a survey, whose NAVTEX navigational warnings apply, and whether a route that avoids contested zones is commercially viable. For the energy side of the story, see Energy Corridors Through Türkiye.

Key Players & Positions

Greece

According to the Greek Ministry of Foreign Affairs, Greece holds that its islands, including Kastellorizo, Rhodes, Karpathos, Kasos and Crete, generate a full continental shelf and EEZ under UNCLOS, which Athens treats as reflecting customary international law. Athens says the only legitimate dispute with Türkiye is the delimitation of the continental shelf and EEZ in the Aegean and Eastern Mediterranean, and that it should be resolved by agreement or referred to the International Court of Justice. Greece regards the 2019 Türkiye–Libya memorandum as legally void because it disregards Greek islands lying between the two coasts, and it points to its 2020 partial agreement with Egypt as a lawful delimitation. Greece has also developed its own national maritime spatial planning framework, and its officials argue that cables between Greek territory and Cyprus lie within Greek and Cypriot sovereign rights, so a state without a delimited claim there cannot require consent.

The Republic of Cyprus

The Republic of Cyprus is internationally recognized as the government of the whole island, a status Türkiye does not accept. Nicosia states that it has sovereign rights over an EEZ declared in 2004 and delimited through bilateral agreements with Egypt, Lebanon and Israel, and that these rights accord with UNCLOS. It says hydrocarbon revenues belong to all Cypriots and would benefit both communities in the context of a settlement, and it rejects any role for Türkiye as a party to delimitation in waters it considers Cypriot. Cyprus also seeks to anchor itself in European energy and connectivity infrastructure, including electricity and data links to Greece.

Egypt

Egypt is a party to UNCLOS and has delimited its EEZ with Cyprus (2003) and, partially, with Greece (2020). Cairo has said that the 2019 Türkiye–Libya memorandum has no legal effect on Egyptian rights. Egypt and Türkiye have worked to restore political relations since 2021–2022, and the presidents met in Cairo in February 2024, but the two states have not concluded any maritime delimitation agreement. Egypt's stake is practical: it hosts LNG facilities and interconnection projects, and a large share of shipping passes through its canal.

The European Union

The European Council has declared its solidarity with Greece and Cyprus on several occasions. Its December 2019 conclusions said the Türkiye–Libya memorandum infringes on the sovereign rights of third states, does not comply with the law of the sea and cannot produce legal consequences for third states. EU institutions generally describe delimitation as a matter for the states concerned under international law, while the EU treats its members' maritime zones as part of its external border and energy security. A map circulated in 2020 and drawn from an academic study by University of Seville researchers, known as the Seville Map, is widely cited in the debate. It assigns Türkiye a restricted zone in the Gulf of Antalya, and Ankara refuses to treat it as legal authority.

Libya and other coastal states

The 2019 memorandum was signed by Libya's Tripoli-based government of the time. Libyan authorities in the east, including the House of Representatives, have contested its validity, and the domestic politics around it remain unresolved. Israel and Lebanon, both with offshore gas interests, also treat Cyprus's agreements with them as binding on their own zones. Lebanon, notably, has not completed ratification of its 2007 agreement with Cyprus.

🇹🇷 Official Policy · Primary Sources

Türkiye's Position

According to Turkish official sources, Ankara's approach rests on two pillars: delimitation of maritime jurisdiction areas on the principle of equity, and protection of the equal and inherent rights of the Turkish Cypriots over the island's offshore resources. In summary:

• Equity, not island projection, decides the line. The Turkish Ministry of Foreign Affairs argues that, in a semi-enclosed sea, islands close to a mainland coast cannot be allowed to cut off the mainland's maritime projection. Ankara cites the Anglo-French arbitration, Libya/Malta and later ICJ jurisprudence as support for reduced or no effect for small islands, and notes that Türkiye has the longest coastline in the basin, about 870 km. The legal basis is the equity principle in customary law of delimitation, and Türkiye's persistent objection to the UNCLOS islands regime.
• Registered coordinates and bilateral agreements. Türkiye has submitted continental shelf coordinates to the UN since 2004 and registered its outer limits there on 18 March 2020. It concluded the Türkiye–TRNC continental shelf delimitation agreement of 21 September 2011 and the Türkiye–Libya memorandum of 27 November 2019. Ankara regards these as lawful exercises of sovereign rights under the principle of equity and says it will continue to take steps to protect them, including licensed exploration by TPAO and drilling by the national fleet (the vessels Fatih, Yavuz, Kanuni and Abdülhamid Han, and the survey ship Oruç Reis).
• Rejection of the Seville Map and of EU competence. Türkiye says the Seville Map reflects a maximalist Greek and Greek Cypriot thesis that confines Türkiye to a narrow strip in the Gulf of Antalya, and that the EU has no competence to adjudicate maritime delimitation in the name of Union solidarity. According to the Turkish Foreign Ministry, only the coastal states concerned, by agreement or by a competent court with the consent of both sides, can delimit their zones. Ankara also objects to Cyprus's agreements with Egypt (2003), Lebanon (2007) and Israel (2010), arguing that they ignore Turkish continental shelf rights and the rights of the Turkish Cypriots.
• Institutional step: Marine Spatial Planning. Türkiye announced its Marine Spatial Planning of the Republic of Türkiye on 16 April 2025 and had it recorded with IOC-UNESCO on 12 June 2025. Turkish officials describe this as the first time that Türkiye's position across the Black Sea, Aegean and Mediterranean has been placed on record with a UN body. A Marine Protected Area was designated off Finike, and the Presidential Circular of 24 July 2025 established an Inter-Agency Coordination Board under the Ministry of Foreign Affairs to coordinate implementation. Ankara's argument is that spatial planning is a sovereign administrative act that organizes uses of its own zones, with delimitation of overlaps still left to negotiation.
• Cables and pipelines: consent and cooperation, not a blanket veto. Ankara says it does not oppose subsea cables or pipelines as such, but that projects and surveys in areas where its continental shelf or the Turkish Cypriots' rights overlap with other claims need consultation and, under the logic of UNCLOS Article 79, the consent of the coastal state concerned. The sources for this stance are Turkish Foreign Ministry statements and NAVTEX notices; see also Fact Check: Does Türkiye Block Undersea Cables and Pipelines in the Eastern Mediterranean?. President Erdoğan's 2020 proposal for an Eastern Mediterranean conference including all coastal states and the Turkish Cypriots, and the TRNC's cooperation proposals of 2011, 2012 and 2019, remain, in Ankara's words, on the table.

The Cyprus dimension is covered in more depth in Crossing the Green Line.

Source Comparison

Different sources describe the same facts with different emphases. The table summarizes the main framings; none of the sides is quoted verbatim, and readers should consult each primary source directly.

Issue	Greek and Greek Cypriot framing	EU and Western media framing	Turkish primary-source framing
Island effect	Islands generate full zones under UNCLOS and custom.	Often follows UNCLOS text; EU conclusions back members' sovereign rights.	Equity requires reduced or no effect for islands near a mainland with the longest coast.
Türkiye–Libya memorandum	Void; ignores Crete and other islands.	Infringes third-state rights; no legal effect on third states (European Council, Dec 2019).	Lawful bilateral delimitation between two coastal states with opposite coasts.
Seville Map	Useful illustration of a lawful EEZ outcome.	Cited as an academic study; not an official EU delimitation.	Maximalist; confines Türkiye to the Gulf of Antalya; no legal standing.
Cyprus's EEZ agreements	Lawful under UNCLOS; revenue to benefit all Cypriots in a settlement.	Treats them as valid agreements by an EU member state.	Ignore Türkiye's shelf and Turkish Cypriot equal rights; unilateral.
Seabed surveys and cables	Sovereign right of Greece and Cyprus; Türkiye has no standing to object.	Coverage often describes Turkish naval actions as obstruction.	Consultation and consent are needed in overlap zones; no objection to cables as such.
2025 spatial planning	Unilateral and cannot affect Greek rights.	Often reported as escalation or map-making.	Administrative act recorded with IOC-UNESCO; delimitation left to negotiation.

What to watch next

• Whether Greece and Türkiye move from the calmer climate set by the 2023 Athens Declaration to talks on delimitation, or remain split over whether the agenda is only the continental shelf and EEZ or a wider set of Aegean questions.
• Whether the Inter-Agency Coordination Board in Ankara and national spatial plans elsewhere in the basin are implemented in ways that narrow or widen overlap areas.
• Whether subsea interconnector and data cable projects are re-routed, re-scheduled or consulted on differently, and how insurers and lenders price legal risk on routes in contested waters.
• Whether the Libyan factions settle the status of the 2019 memorandum, which affects the southern edge of the Türkiye–Greece–Egypt triangle.

Key Terms & Related Guides

• Blue Homeland (Mavi Vatan): a Turkish maritime doctrine first articulated in 2006 by Admiral Cem Gürdeniz. It asserts Türkiye's jurisdiction over seas in the Black Sea, Aegean and Eastern Mediterranean, and it is now reflected in official policy documents and in the 2025 spatial planning.
• Continental shelf: the seabed and subsoil extending from a coast, over which the coastal state has exclusive rights to explore and exploit natural resources.
• EEZ (exclusive economic zone): a zone up to 200 nautical miles (about 370 km) from the baselines in which the coastal state has sovereign rights over living and non-living resources.
• Equity principle: the rule in delimitation law that the result must be equitable, taking account of coastal geography, the length of coasts and proportionality.
• Seville Map: a map circulated in 2020 and drawn from a University of Seville study; Greece and the Greek Cypriots treat it as illustrative, while Türkiye rejects it as maximalist.
• Marine Spatial Planning (MSP): a national plan for organizing uses of sea areas. Türkiye's was announced on 16 April 2025 and recorded with IOC-UNESCO on 12 June 2025.
• NAVTEX: a maritime safety information system through which states announce exercises, surveys and drilling, often a first indicator of friction.
• TRNC: the Turkish Republic of Northern Cyprus, recognized only by Türkiye; the Turkish Cypriots are co-founders of the 1960 Republic of Cyprus.

Related reading on Recorridor:

• The Crossroads Guide: How Türkiye's Straits, Rail Lines and Ports Connect Europe and Asia
• Energy Corridors Through Türkiye
• Freedom of Passage Under Montreux
• Fact Check: Does Türkiye Block Undersea Cables and Pipelines?
• Recorridor: Türkiye's Crossroads of Straits, Corridors and Borders, Explained

Related analyses from sister publications:

• Doctrine Review: Eastern Mediterranean Maritime Jurisdiction: Continental Shelf, EEZ and the Blue Homeland
• The Global Anatomy: The Seville Map Explained
• The Nations Compass: Fact Check: Is Türkiye Violating UNCLOS in the Eastern Mediterranean?
• Monitor of Nations: Blue Homeland and the Eastern Mediterranean: Maritime Jurisdiction, Equity and the Law of the Sea

For how Recorridor handles sources and positions, see the Editorial Principles and the About page.

Recorridor presents global and regional affairs with a dedicated perspective from Türkiye. Sections marked 'Türkiye's Position' reflect official Turkish policy and legal doctrines as stated by Turkish primary sources.