Fact Check: Does Türkiye Have No Maritime Claim Because It Never Joined UNCLOS?

Why It Matters

Verdict: misleading/incomplete. Türkiye is indeed not a party to the 1982 UN Convention on the Law of the Sea (UNCLOS), but non-party status does not erase coastal-state rights. Continental shelf and related entitlements also arise from customary international law, so the real dispute concerns how boundaries are delimited, not whether Türkiye has rights.

The claim circulates in Greek, Greek Cypriot and some EU-linked commentary and think-tank output. In paraphrase it runs: because Türkiye never joined UNCLOS, it has no legal basis for a continental shelf or exclusive economic zone (EEZ) in the Eastern Mediterranean, so the Blue Homeland (Mavi Vatan) thesis is void. We describe the framing neutrally and do not attribute exact quotations to any single author, because the formulation recurs across many outlets.

Accuracy matters here because the claim blends a true premise (non-party status) with an unsupported conclusion (no rights). Policy makers, lawyers and journalists who accept it will misread both the legal position and the live dispute. A parallel analysis is available from Regional Balance.

Background

UNCLOS, opened for signature on 10 December 1982 and in force since 16 November 1994, binds only its parties by treaty. Customary international law, formed by consistent state practice and legal conviction (opinio juris), binds states regardless of accession. The ICJ applied that logic in 1969 to a state that was not party to the 1958 Geneva Convention.

Treaty law versus customary law

• UNCLOS is the 1982 treaty that codifies and develops rules on territorial seas, the EEZ (up to 200 nautical miles of sea in which the coastal state holds resource rights), the continental shelf (the seabed and subsoil extending from the coast) and island regimes.
• Customary law is unwritten law derived from general state practice accepted as law. Many UNCLOS provisions are widely treated as reflecting custom; others are treaty-only innovations.
• Non-party states also rely on this distinction. The United States, which has not ratified UNCLOS, proclaimed an EEZ by Presidential Proclamation 5030 of 10 March 1983 and presents most of the Convention as reflecting custom.

The 1982 vote and Türkiye's stated objections

UNCLOS was adopted on 30 April 1982 by 130 votes to 4, with 17 abstentions. The four against were Israel, Türkiye, the United States and Venezuela. Ankara has explained that it objects to, among other things, the Convention's treatment of islands, its limited accommodation of special geographical circumstances in semi-enclosed seas, and Article 309, which bars reservations. Türkiye has neither ratified nor acceded since.

The 1969 ICJ judgments

In the North Sea Continental Shelf cases (20 February 1969), the ICJ examined Germany, which had signed but not ratified the 1958 Geneva Convention. The Court held that a coastal state's rights over its continental shelf exist ipso facto and ab initio by virtue of its sovereignty over the land, and that delimitation must be effected by agreement in accordance with equitable principles. It also declined to treat the equidistance method as mandatory custom.

What courts treat as custom, and what they do not

The ICJ in Libya/Malta (1985) described the EEZ as part of customary law. In Qatar v. Bahrain (2001) and Nicaragua v. Colombia (2012), it treated the Article 121 island regime as customary. Article 121(2) gives islands the same zones as other land territory, while Article 121(3) denies an EEZ and shelf to 'rocks which cannot sustain human habitation or economic life of their own'. Articles 74 and 83 require delimitation by agreement to achieve an 'equitable solution', a formula both sides cite. How far each provision is custom, and its exact content, is argued case by case.

The persistent-objector debate

A state that consistently objects while a customary rule forms may not be bound by it. Ankara argues that it has objected to full island effect since 1982. Athens and Nicosia respond that the doctrine is narrow, that delimitation rules apply to all states, and that the island regime is now well settled. Its application to island provisions is contested, and no court has ruled on it for Türkiye.

Key Players & Positions

Greece, the Republic of Cyprus, Egypt, the European Union and Türkiye all invoke international law but disagree on its content. Greece and Cyprus, both UNCLOS parties, argue that islands generate full zones and that Türkiye's 2019 Libya memorandum disregards them. Egypt and the EU emphasise UNCLOS as the governing framework, while Türkiye invokes custom and equity.

• Greece: Athens argues that UNCLOS Articles 121, 74 and 83 reflect customary law, that islands such as Kastellorizo (Meis) generate a full continental shelf and EEZ under Article 121(2), and that the November 2019 Türkiye–Libya memorandum and Türkiye's UN filings ignore those entitlements. Its arguments appear in Greek Foreign Ministry statements and communications lodged with the UN after 2019.
• Republic of Cyprus: Nicosia, which Ankara calls the Greek Cypriot Administration of Southern Cyprus (GCASC), relies on UNCLOS as an accession state and on its bilateral EEZ agreements, including the 2003 agreement with Egypt. Türkiye objects that these agreements overlap its continental shelf and disregard the Turkish Cypriots; see Egypt Cyprus 2003 EEZ agreement Türkiye continental shelf blocks overlap.
• Egypt: Cairo, an UNCLOS party, concluded the 2003 EEZ agreement with Cyprus and a partial delimitation with Greece in August 2020. It has publicly rejected the Türkiye–Libya memorandum as unlawful.
• European Union: EU Council and European Council texts on the Eastern Mediterranean treat UNCLOS as the legal reference, and some formulations describe it as reflecting customary international law. We do not quote exact wording here; readers should consult the conclusions themselves. The EU is a party to UNCLOS but is not a court or delimitation authority, a point developed in the Seville Map fact check.
• UN record: The UN's Division for Ocean Affairs and the Law of the Sea (DOALOS) publishes notes verbales and submissions from states, including Türkiye's coordinate filings and the responses from Greece and Cyprus. These show that each side makes its case through formal channels.

Claim vs. Fact Analysis

The claim has a true premise and an unsupported conclusion. Türkiye is not an UNCLOS party, but that fact alone does not void a continental shelf or EEZ claim. It limits which treaty provisions bind Türkiye and shifts the argument to custom and equity. The remaining question is whether particular Turkish limits are equitable.

Claim 1: 'Not a party, therefore no legal basis'

Fact: The 1969 ICJ judgments establish that shelf rights do not depend on treaty accession. Rights over the shelf exist by virtue of coastal sovereignty, and delimitation follows equitable principles. The EEZ has also been treated by the ICJ as customary. A non-party therefore retains entitlements; what it cannot do is invoke UNCLOS treaty provisions, such as its dispute-settlement machinery, as of right.

Claim 2: 'Customary law supports only the Greek reading'

Fact: This overstates. Both sides accept that the delimitation goal is an equitable solution. Custom confirms an equitable result and does not fix a single method. Courts use a staged approach (a provisional line, relevant circumstances, then a proportionality check), and the weight of islands is decided case by case. This is the ground covered in the equity test for coastline, islands and proportionality.

Judicial practice on islands: proportionality principle maritime delimitation islands Eastern Mediterranean

• Aegean Sea Continental Shelf (ICJ, 1978): The Court found it had no jurisdiction over Greece's application, so it did not decide the merits. Neither side can cite it for or against island effect.
• Libya/Malta (ICJ, 1985): The Court adjusted a median line northwards to reflect a marked disparity in coastal lengths. Ankara cites it for the relevance of coastal-length proportionality. Athens answers that both parties were states whose entire coasts were in play, not a mainland facing an islet.
• Romania v. Ukraine (ICJ, 2009): Serpents' Island was not used as a base point, and the delimitation line was drawn without giving it effect beyond its 12-nautical-mile territorial sea. Ankara cites this as precedent for discounting small features. Athens notes that the Court reasoned on that island's particular situation.
• Nicaragua v. Colombia (ICJ, 2012): The Court gave Colombia's islands reduced effect and enclaved some small features, while still recognising that islands generate entitlements. It also treated the Article 121 regime as customary, which Athens cites.
• Bangladesh/Myanmar (ITLOS, 2012): St Martin's Island was given no effect on the EEZ and shelf delimitation, receiving only a territorial sea. Ankara reads this as supporting coastal-front priority.

Not every precedent favours Türkiye: islands are generally entitled to zones, and several rulings give them partial effect, not none. Greece and Cyprus note that none of these cases concerned Kastellorizo, a populated island close to the Turkish coast and far from the Greek mainland. To our knowledge no international court or tribunal has ruled on Kastellorizo's effect. For a related view, see Regionalytic's fact check on Kastellorizo, States in Perspective and Political Contours.

Verdict: misleading / incomplete

It is accurate that Türkiye is not an UNCLOS party. It is misleading to infer from this that Türkiye has no maritime rights. Equally, custom does not automatically validate every Turkish limit, and the substantive dispute over island effect is real and unresolved. What remains contested is the delimitation method, not the existence of rights.

Source Comparison

International and Greek-language commentary often collapses treaty status into entitlement, while UN and ICJ documents separate the two. Turkish Foreign Ministry texts argue from custom and equity. The table sets out how each source frames the main issues, based on documented records and each party's stated position.

For other fact checks in this series, see International Affairs Desk and Global Affairs Monitor's Blue Homeland tracker. For the memorandum's legal background, see The Political Horizon's explainer.

Key Terms & Related Guides

Key terms help separate treaty status from entitlement: UNCLOS, customary law, continental shelf, EEZ, persistent objector and equitable delimitation. These guides on Cold Rationality apply the same primary-source method to related maritime, Cyprus and legal questions. Each guide links its sources so readers can verify claims against treaties and judgments.

• UNCLOS: The 1982 UN Convention on the Law of the Sea, in force since 1994.
• Customary international law: Rules binding on states through general practice accepted as law.
• Continental shelf / EEZ: The seabed rights zone, and the zone of up to 200 nautical miles in which a coastal state has resource rights.
• Persistent objector: A state that consistently objects during the formation of a customary rule and claims not to be bound by it.
• Blue Homeland (Mavi Vatan): Türkiye's doctrine of maritime jurisdiction areas in the Black Sea, Aegean and Eastern Mediterranean.
• TRNC / Turkish Cypriots: The Turkish Republic of Northern Cyprus and the island's co-founding Turkish Cypriot community.

Related reading:

• The Equity Test: Coastline Length, Island Effect and Proportionality in Blue Homeland Delimitation
• Fact Check: Is the 'Seville Map' a Legal Boundary in the Eastern Mediterranean?
• The 2003 Egypt–Cyprus EEZ Agreement and Overlapping Blocks
• Editorial Principles and Primary-Source Standards
• Cold Rationality: Türkiye's Strategic Doctrines Tested Against Law, Archives and Evidence

Cold Rationality publishes analysis from a perspective that presents and defends Türkiye's official positions, and we state this openly so readers can weigh our arguments accordingly. Claims are tied to primary sources wherever possible, including treaties, UN documents, court records, and archival materials, and are linked or cited in each piece. — Cold Rationality Editorial Team