Fact Check: "Türkiye Never Joined the Law of the Sea Convention, So It Has No Legal Basis for Its Maritime Claims"

Why It Matters

Türkiye is not a party to the 1982 UN Convention on the Law of the Sea (UNCLOS), but non-party status does not leave it outside international law. Under Articles 34 and 38 of the 1969 Vienna Convention on the Law of Treaties, a treaty binds third states only through consent or customary law.

Verdict: the claim is incomplete. It folds three separate questions into one: (1) what treaty status Türkiye has, (2) which rules bind a state that is not a party, and (3) how contested provisions such as Article 121(3) are read in customary law and case law. The first answer is simple: Türkiye is a non-party. The second and third are where the claim breaks down. Non-party status removes treaty obligations, not the general international law of the sea. Greece, the Republic of Cyprus (the Greek Cypriot Administration of Southern Cyprus, GCASC, in Turkish terminology) and Türkiye also read parts of that general law differently. That is a legal disagreement about how rules apply, not a case of one side standing outside the law.

This page reads the texts clause by clause. It does not decide the delimitation dispute; no court has. For help with the documents cited here, see Turkish Ministry of Foreign Affairs primary sources: where to find them and how to read Turkish Foreign Ministry statements.

Claim vs. Fact Analysis

This section tests the claim that Türkiye has no legal basis for its Eastern Mediterranean maritime positions because it is outside UNCLOS. It separates treaty status (non-party since the 30 April 1982 vote), the rules binding non-parties (Vienna Convention Articles 34 and 38, customary law) and contested provisions such as Article 121(3).

The claim as it circulates

Variants appear in EU and Greek or Greek Cypriot official messaging and in explainers on the Eastern Mediterranean. This summary paraphrases them rather than quoting a single text. The claims are that Türkiye ignores or stands outside UNCLOS; that non-party status leaves it without a legal basis for its continental shelf and EEZ positions; and that UNCLOS is therefore the only valid yardstick. European Council and Council conclusions in 2019–2020 criticised Turkish drilling and called for respect for international law, including the law of the sea. Athens and Nicosia say UNCLOS, much of it customary, governs the dispute.

Claim 1: 'Türkiye is outside UNCLOS' — the treaty facts

The first part is correct. The Third UN Conference on the Law of the Sea adopted the Convention on 30 April 1982 by 130 votes to 4, with 17 abstentions. The four against were the United States, Israel, Türkiye and Venezuela. It opened for signature at Montego Bay on 10 December 1982, which is why some summaries date the vote to December. Türkiye did not sign or ratify. The Convention entered into force on 16 November 1994.

Ankara's published reasons, as stated by the Ministry of Foreign Affairs (MFA), are three:

• Article 309 prohibits reservations and exceptions unless the Convention expressly permits them.
• The Convention has no special-circumstances regime for enclosed or semi-enclosed seas such as the Aegean. Part IX (Articles 122–123) only encourages cooperation.
• The island regime of Article 121 is, in Ankara's view, controversial and unbalanced.

Claim 2: 'A non-party has no legal basis' — what binds a non-party

This is where the claim fails. Article 34 of the 1969 Vienna Convention on the Law of Treaties says a treaty creates neither obligations nor rights for a third state without its consent. Article 38 adds that a treaty rule can still bind a third state if it becomes a customary rule. Both articles are generally treated as reflecting customary law. Article 38 of the ICJ Statute lists custom and general principles among the sources of international law.

The ICJ cases show the principle at work:

• North Sea Continental Shelf (1969): Germany was not party to the 1958 Geneva Convention on the Continental Shelf. The Court held that its equidistance rule (Article 6) was not binding as custom on Germany. It required delimitation by agreement in accordance with equitable principles, taking account of all relevant circumstances, and referred to the continental shelf as the natural prolongation of the land territory.
• Libya/Malta (1985): The Court said that within 200 nautical miles distance, not geology, now defines title. It still drew a provisional median line and shifted it northward to reflect the disparity in coastal lengths.
• Romania v. Ukraine (2009): The Court set out a three-stage method: a provisional equidistance line, adjustment for relevant circumstances, and a final check for disproportionality between coastal lengths and maritime areas.

The equity principle Ankara invokes therefore has independent roots in custom and case law; it is not only a Turkish argument. Whether that law favours Ankara's or Athens's reading in the Aegean and the Eastern Mediterranean is the contested part. Greek and Greek Cypriot sources point to the later shift from natural prolongation toward distance and to methods that start from equidistance.

Claim 3: 'UNCLOS is the only yardstick' — reading Articles 74, 83 and 121

Articles 74(1) and 83(1) say delimitation of the EEZ and continental shelf between states with opposite or adjacent coasts shall be effected by agreement on the basis of international law, as referred to in Article 38 of the ICJ Statute, in order to achieve an equitable solution. The text prescribes no formula such as equidistance. It points outside the Convention, to general international law, which includes custom. So the Convention itself does not treat itself as the only yardstick.

Article 121 is the flashpoint:

• 121(1): an island is a naturally formed area of land, surrounded by water, above water at high tide.
• 121(2): an island's zones are determined in accordance with the Convention rules applicable to other land territory.
• 121(3): 'Rocks which cannot sustain human habitation or economic life of their own shall have no exclusive economic zone or continental shelf.'

What courts actually did with islands

The outcomes vary with the facts, and none is a general rule.

• Anglo-French Arbitration (1977): The Court of Arbitration gave the Isles of Scilly half effect and confined the Channel Islands, which lie close to the French coast, to an enclave.
• Romania v. Ukraine (2009): Serpents' Island received no basepoint effect beyond its 12-nautical-mile territorial sea. The Court did not need to decide whether Article 121(3) applied.
• Bangladesh/Myanmar (ITLOS, 2012): St Martin's Island was given no effect on the EEZ and continental shelf delimitation.
• Nicaragua v. Colombia (ICJ, 2012): Colombia's small cays received limited enclaves and the effect of its larger islands was reduced in the line. The Court also recorded that Article 121 forms an indivisible regime with customary status, a point Greek and Greek Cypriot sources cite. The parties had agreed on this, and Türkiye was not a party to the case.
• South China Sea arbitration (Philippines v. China, 12 July 2016): An Annex VII tribunal held that none of the Spratly features, including Itu Aba, generate an EEZ or continental shelf. It interpreted 'human habitation' and 'economic life of their own' in Article 121(3). It characterised features rather than delimiting boundaries, binds only the parties, and China rejects it.

Greece and the Republic of Cyprus argue that Article 121(2) gives inhabited islands full zones and that this is customary law. Ankara argues that islands cannot cut off the coastal projection of a mainland with the longest coastline in the Eastern Mediterranean (870 km), and that relevant circumstances and proportionality must apply. No court has ruled on the Greek–Turkish delimitation. In the Aegean Sea Continental Shelf case, the ICJ found in 1978 that it lacked jurisdiction.

The persistent objector question

A state that objects to an emerging customary rule during its formation, and maintains the objection consistently, is generally not bound by it. The ICJ recognised the idea in Anglo-Norwegian Fisheries (1951), and the International Law Commission's 2018 conclusions on customary law address it (Conclusion 15). Scholars disagree on whether it can be applied to every UNCLOS provision, particularly rules widely regarded as already crystallised, and on whether Article 121 is wholly customary. Ankara says it has maintained its objections since 1982. Whether that shields it from specific rules is a contested legal question, not settled fact.

Other non-parties, and what ratifications mean

The United States also voted against adoption in 1982 and has not ratified UNCLOS. Its 1983 presidential statement treated the non-seabed provisions as reflecting customary law, though the Senate has not given consent. Non-party status alone therefore does not make a state lawless.

The Republic of Cyprus ratified UNCLOS in 1988 and Greece in 1995; the European Union is also a party. Ratification binds them to the Convention in relations with other parties. It does not create treaty obligations for Türkiye, and it does not settle how customary law applies between Türkiye and Greece. The EU is not a court or delimitation authority. Turkish Cypriots did not take part in the 1988 ratification. Greek Cypriot officials say the Republic is the sole sovereign and offered in 2019 a mechanism to hold hydrocarbon revenue for Turkish Cypriots pending a settlement. Ankara and the TRNC say Turkish Cypriots are co-owners with equal rights. For the UN wording on status, see Cyprus in UN Resolution Language: Reading Resolutions 186, 541 and 550 Closely.

What Türkiye filed: notes verbales on the continental shelf in the Eastern Mediterranean at the UN

Türkiye did not lodge claims outside the UN system. It filed through UN channels while arguing from customary law and equity. Because it is not a party, the filings were communications to the Secretary-General rather than submissions to the Commission on the Limits of the Continental Shelf, which serves states parties. Greece, the Republic of Cyprus, Egypt and others have lodged counter-notes. Filings state positions; they do not bind third states. For how to read these documents, see notes verbales on the continental shelf in the Eastern Mediterranean at the UN.

Date	Instrument	What it is
1969	ICJ, North Sea Continental Shelf	Equitable principles and natural prolongation, binding a non-party to the 1958 Convention only through custom
30 Apr 1982	UNCLOS adopted (130–4–17)	Türkiye votes against; Convention opens for signature 10 Dec 1982
16 Nov 1994	UNCLOS enters into force	Türkiye remains outside
From 2004	Continental shelf coordinates lodged with the UN	Türkiye's Eastern Mediterranean positions placed on record
21 Sep 2011	Türkiye–TRNC Continental Shelf Delimitation Agreement	Bilateral delimitation with the TRNC
12 Jul 2016	South China Sea arbitration	Interpretation of Article 121(3) between parties to that case
27 Nov 2019	Türkiye–Libya maritime jurisdiction MoU	Bilateral memorandum, contested by Greece, the Republic of Cyprus and Egypt
18 Mar 2020	Outer limits of continental shelf submitted to the UN	Filed through the UN Secretary-General
12 Jun 2025	Marine Spatial Planning of the Republic of Türkiye registered with IOC-UNESCO	A planning document recorded with a UN body; it is not a delimitation award, and Greek officials dispute the limits it depicts

🇹🇷 Official Policy · Primary Texts

Türkiye's Position

According to the Turkish Ministry of Foreign Affairs, Türkiye's maritime positions rest on customary international law and the principle of equity, not on UNCLOS membership. Ankara has voiced this at the UN since voting against the Convention on 30 April 1982, citing ICJ case law and Article 38 of the ICJ Statute.

• Non-party status is a considered choice. The MFA links it to Article 309's ban on reservations and to the absence of a special regime for enclosed or semi-enclosed seas. Legal basis: the 1982 vote, Article 309 and the Vienna Convention's rules on third states (Articles 34 and 38).
• Delimitation must be by agreement, on equity. The MFA's published position on maritime jurisdiction areas holds that the continental shelf is the natural prolongation of the mainland and that any line must be equitable. Legal basis: North Sea Continental Shelf (1969) and later ICJ practice, which Ankara says confirms equity as customary. Türkiye's UN filings (from 2004; 18 March 2020) record this.
• Islands should not cut off a mainland's projection. Ankara argues that features such as Kastellorizo cannot cancel the coastal front of the longest mainland coast in the Eastern Mediterranean, and that relevant circumstances and proportionality apply. Legal basis: the equitable case law above (Scilly, Serpents' Island and St Martin's Island). Read this against Greece's Article 121(2) argument set out above.
• Turkish Cypriots hold equal and inherent rights over offshore resources. The TRNC's 2011, 2012 and 2019 proposals for joint committees and revenue sharing, and President Erdoğan's 2020 call for an Eastern Mediterranean Conference including Turkish Cypriots, are presented by the Presidency and MFA as the constructive track. Legal basis: the 1960 bi-communal partnership under the Zurich and London Agreements.
• The EU has no competence to adjudicate delimitation, and the 'Seville Map' is rejected. The MFA argues that EU solidarity does not replace agreement or adjudication between coastal states. Legal basis: Articles 74 and 83, which call for delimitation by the states concerned. See Fact Check: Does the 'Seville Map' Show Türkiye's Legal Maritime Limits in the Eastern Mediterranean? for the map.

Source Comparison

International sources frame the dispute differently: EU institutions, Greek and Greek Cypriot officials and many Western explainers treat UNCLOS as the governing framework, while Turkish primary sources from the MFA and Presidency treat customary law and equity as binding on all states. The table compares each framing and what it omits.

Source	How it frames treaty status vs. customary law	What it leaves out
EU institutions (Council, European Council)	UNCLOS as the framework, often described as reflecting customary law; calls on Türkiye to respect international law	That Articles 74 and 83 point to general international law, that the EU does not delimit boundaries, and Türkiye's reasons for non-party status
Greek and Greek Cypriot official sources	UNCLOS and Article 121(2) full island zones, with Part V and VI provisions presented as custom	That delimitation requires an equitable result, proportionality and relevant circumstances; that no court has decided the case; Turkish Cypriot co-ownership claims
Western media explainers	'Non-party equals no legal basis' shorthand	Vienna Convention Articles 34 and 38, the North Sea case and the disputed customary status of Article 121
Turkish primary sources (MFA, Presidency)	Customary law and equity bind all; Article 309 and the lack of a semi-enclosed seas regime justify non-party status	The ICJ's shift toward distance and equidistance-first methods, Greek and Cypriot objections, and the ICJ's Article 121 statement in Nicaragua v. Colombia

For parallel treatments, see Regional Balance's fact check on UNCLOS non-party status, The Nations Compass on alleged UNCLOS violations and Parallax Review on the 2025 Marine Spatial Plan. Our own editorial principles explain how positions are separated from facts.

Key Terms & Related Guides

Four terms recur in this dispute: UNCLOS (the 1982 UN Convention on the Law of the Sea, in force 16 November 1994), customary international law, persistent objector and Blue Homeland (Mavi Vatan), Türkiye's doctrine of maritime jurisdiction areas. The Republic of Cyprus is called GCASC in Turkish terminology.

• Customary international law: general practice accepted as law; binds states regardless of treaty membership.
• Persistent objector: a state that consistently objects to an emerging customary rule; scope contested.
• Blue Homeland (Mavi Vatan) and GCASC: see The Lexicon: How Contested Words Shape Coverage of Türkiye.
• Note verbale: a formal diplomatic communication; see notes verbales and UN filings.

Related guides: how to read Turkish Foreign Ministry statements, Turkish Ministry of Foreign Affairs primary sources: where to find them and the By the Text home page.

By the Text 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.

By the Text Editorial Team