Fact Check: Is Türkiye Violating UNCLOS in the Eastern Mediterranean?

Why It Matters

Verdict: Misleading / Imprecise. Türkiye did not sign or ratify the 1982 UN Convention on the Law of the Sea (UNCLOS), so it cannot 'violate' a treaty it never joined. The accurate version of the claim is narrower: Greece, the Republic of Cyprus and the European Union argue that key UNCLOS rules are customary law binding on every state, while Ankara argues that customary law requires equitable delimitation and does not give distant islands full weight against the longest continental coastline in the Eastern Mediterranean. Getting this distinction right decides which legal tests, and which court precedents, apply.

Background

Where the claim comes from

The claim circulates in a familiar form: 'Türkiye is breaking UNCLOS / refuses to follow international maritime law.' It appears in statements by Greece and by the Republic of Cyprus (the Greek Cypriot administration, abbreviated GCASC in Turkish usage), in European Council conclusions, and in think-tank commentary. A frequently cited example is the European Council conclusions of December 2019, which said the Türkiye–Libya memorandum of understanding 'does not comply with the Law of the Sea' and cannot produce legal consequences for third states. Readers should check the full text on the Council's website. Greek and Greek Cypriot foreign-ministry statements make similar arguments in their own words, and this article paraphrases them rather than quoting.

What 'party to a treaty' means

A treaty binds the states that consent to it by ratification or accession. A widely accepted principle, reflected in Article 34 of the 1969 Vienna Convention on the Law of Treaties, is that a treaty does not create obligations for a third state without its consent. The facts on UNCLOS are:

• UNCLOS was adopted in 1982 and entered into force on 16 November 1994.
• The UN Treaty Collection lists roughly 170 parties, including the European Union. Greece, the Republic of Cyprus, Egypt and Lebanon are among them.
• Türkiye and Israel are not parties. Türkiye was among the four states that voted against adoption on 30 April 1982 (recorded vote 130–4–17), and it did not sign the Convention.
• Article 309 prohibits reservations and exceptions unless expressly permitted. The Convention is therefore a package that a state must accept or decline as a whole.
• Article 121(2) says islands generate maritime zones like other land territory, while Article 121(3) says rocks that cannot sustain human habitation or economic life of their own have no EEZ or continental shelf.
• Articles 74 and 83 require delimitation by agreement 'on the basis of international law' to reach an 'equitable solution'.

Short chronology

• 1969: the ICJ decides North Sea Continental Shelf.
• 2003, 2007, 2010: the Republic of Cyprus signs EEZ agreements with Egypt, Lebanon and Israel.
• 21 September 2011: Türkiye and the TRNC sign a continental shelf delimitation agreement.
• 27 November 2019: Türkiye and Libya sign a maritime jurisdiction memorandum.
• 18 March 2020: Türkiye registers the outer limits of its continental shelf with the UN.
• 12 June 2025: Türkiye's Marine Spatial Planning is registered with IOC-UNESCO.

Claim vs. Fact Analysis

Claim 1: 'Türkiye is violating UNCLOS'

Fact: Türkiye has no treaty obligation under UNCLOS, so a treaty violation in the strict sense cannot arise. UNCLOS's compulsory dispute-settlement procedures (Part XV) operate between states parties, and no court or tribunal has ruled that Türkiye breached the Convention. What neighbours can legitimately allege is a different claim: that Turkish activities infringe their sovereign rights under customary international law. That is a contestable legal argument and a different claim from the one commonly stated in headlines.

What is accurate: Turkish seismic and drilling activities, and the 2019 Libya memorandum, are firmly contested by Greece, the Republic of Cyprus, Egypt and the EU.

Claim 2: 'UNCLOS is customary law, so non-party status is irrelevant'

Greek and Greek Cypriot view, stated fairly: Articles 74, 83 and 121 reflect customary law binding on all states. In Nicaragua v. Colombia (2012) the ICJ said the regime of islands in Article 121 forms an indivisible regime with customary status. On this reading, islands, including Greek ones, may generate full continental shelf and EEZ entitlements.

Turkish counter-view: Custom is not identical to treaty text. Ankara argues that it objected to the Convention's approach to islands during UNCLOS III, voted against adoption, never signed, and is therefore a persistent objector to provisions it regards as incompatible with equity. The ICJ has recognised the persistent-objector doctrine in principle (Fisheries, 1951), but it has not ruled on whether it applies to Türkiye in this region. Critics note that the doctrine requires an objection that is timely and consistent, and that it is difficult to maintain against widely accepted rules. This is a genuine point of law and not a settled fact either way.

Claim 3: 'There is a clear legal answer on islands'

The ICJ's own case law shows that the rules everyone accepts are equitable principles and relevant circumstances, and that island effect varies:

• North Sea Continental Shelf (1969): Germany, not bound by the 1958 Geneva Convention's equidistance rule, was held to be bound only by equitable principles. Delimitation was to be effected by agreement, taking relevant circumstances into account and avoiding the cut-off of a state's natural prolongation.
• Tunisia/Libya (1982): equitable principles and relevant circumstances governed, and the Kerkennah Islands received reduced (half) effect.
• Libya/Malta (1985): the median line was adjusted to reflect, among other factors, the disparity in coastal lengths.
• Romania v. Ukraine (2009): Serpent Island was given no effect on the continental shelf and EEZ line beyond its territorial sea, and the Court checked the result for proportionality.
• Nicaragua v. Colombia (2012): Colombia is not an UNCLOS party, yet the Court applied customary law and limited the effect of small islands.

The Greek and Cypriot side replies that these cases concerned tiny or marginal features, and that large inhabited islands such as Crete and Rhodes stand in a different category. It also cites the 2016 South China Sea arbitral award on Article 121(3), which binds only the parties to that case. Türkiye answers that Kastellorizo (Meis), about 2 km (1.2 miles) off its coast and far from the Greek mainland, is exactly the kind of case where full effect would produce an inequitable result. The debate is therefore about the weight of islands and proportionality, not about whether law applies.

Claim 4: 'Not being a party means Türkiye is outside the law' (or 'proves it is innocent')

Both versions are wrong. The United States and Israel are also outside UNCLOS, and Colombia signed but did not ratify it. The United States states that it treats most of the Convention as reflecting customary law, and the ICJ applied customary law to Colombia. Non-party status therefore removes treaty obligations but not customary obligations, and it neither proves nor disproves any specific violation.

Claim 5: 'Unilateral Turkish claims ignore Cyprus'

The Republic of Cyprus is a UN and EU member and an UNCLOS party. It signed EEZ agreements with Egypt (2003), Lebanon (2007) and Israel (2010), and it states that hydrocarbon revenue would benefit both communities. Ankara and the TRNC reply that Turkish Cypriots, as co-founders of the 1960 state, hold equal rights over the island's resources and were never consulted. They also say the 2003 agreement overlaps areas Türkiye claims as its continental shelf (Blocks 1, 4, 5, 6 and 7). The 21 September 2011 Türkiye–TRNC agreement followed the Greek Cypriot drilling of 19 September 2011, and the TRNC made joint-committee and revenue-sharing proposals in 2011, 2012 and 2019. For the constitutional background, see Cyprus Meridian: The 1960 Treaties and the Case for Sovereign Equality.

Claim 6: 'Türkiye refuses dialogue and rules'

President Erdoğan called in 2020 for an Eastern Mediterranean Conference including all coastal states and the Turkish Cypriots, and Greek–Turkish exploratory contacts resumed in January 2021. On 12 June 2025 Türkiye registered its Marine Spatial Planning with IOC-UNESCO, as explained in Türkiye's Marine Spatial Planning and the 2025 IOC-UNESCO Registration. Critics respond that registering a plan unilaterally does not resolve overlapping claims. Both observations are factually correct, and neither amounts to a treaty violation.

Key Players & Positions

• Greece: says the relevant UNCLOS provisions are customary law and that its islands generate full zones. It also points to its 2020 delimitation agreements with Italy and Egypt.
• Republic of Cyprus (GCASC): presents itself as the sole internationally recognised state on the island and relies on its EEZ agreements.
• European Union: its Council conclusions criticise Turkish drilling and the Libya memorandum, and the EU itself is an UNCLOS party.
• Türkiye: a non-party and objector that calls for equitable delimitation by agreement. See the Blue Homeland guide and The Seville Map Explained: Why Ankara Rejects It.
• TRNC / Turkish Cypriots: claim equal rights to offshore resources.
• Libya and Egypt: Libya signed the 2019 memorandum with Türkiye, and Egypt signed EEZ agreements with Cyprus and later Greece. Both memoranda remain contested.
• ICJ and ITLOS: the neutral reference for how delimitation law is applied.

Source Comparison

What is accurate in the headline: Türkiye's activities and agreements are contested by neighbours and by the EU. What is not: that a treaty Türkiye never joined is being 'violated'. A precise statement would be that Greece and Cyprus contend Türkiye breaches customary law, and Türkiye contests both the content and its binding force. For further context, see Doctrine Review on Eastern Mediterranean maritime jurisdiction, Crossroads Review on the Blue Homeland and The Worldlogue's fact check on the Seville Map.

Key Terms & Related Guides

• UNCLOS: the 1982 treaty that sets maritime zones and delimitation rules for its parties.
• Customary international law: unwritten rules based on consistent state practice accepted as law, which can bind non-parties.
• Persistent objector: a state that objects consistently while a rule is forming and so may not be bound by it. The doctrine is contested in application.
• Continental shelf and EEZ: seabed and water-column rights extending to 200 nautical miles, or less where claims overlap.
• Island effect and proportionality: the weight a feature carries in drawing a boundary, tested against the ratio of coastal lengths.

Related reading: Blue Homeland and the Eastern Mediterranean: Maritime Jurisdiction Explained, The Seville Map Explained, Fact Check: Calibrating the Compass on Claims About Türkiye, Editorial Principles and Primary Source Standards and About The Nation's Compass.

Perspective Note: The Nation's Compass presents global affairs with a dedicated perspective from Türkiye. Sections marked 'Türkiye's Position' reflect official Turkish policy as stated by Turkish government sources. Claims are attributed to treaties, UN documents and court decisions so that readers can verify them independently.

By The Nation's Compass Editorial Team.