Turkey is trying in every way to prevent the implementation of any energy project in the Eastern Mediterranean that bypasses it, whether it is a natural gas pipeline or an electricity transmission cable. Depending on the case, it activates various “tools” at its disposal which always end up in a common denominator: the (direct or indirect) intimidation of investors and states and the threat of using force or the direct projection of power. Sometimes it propagates objections of an economic and technical nature in order to damage the viability of a project (like the EastMed pipeline – the project to transport natural gas from East Mediterranean gas fields to Italy and Central Europe through Greece) or sends warnings by expelling ships that conduct research at an early stage or even conducts its own seismic surveys and drilling to demonstrate its alleged rights, to discourage the parties involved altogether.
Wanting to dominate its wider neighborhood, Ankara does not understand that it will not have a say and role in partnerships that forge relationships, change balances and bring stability and prosperity. At the same time, it envisions its transformation into the energy hub of Europe and has spent over 1 billion dollars to have more flexibility in its actions, without requiring the renting of equipment from other countries and even for actions outside international legality. As a result of these perceptions, Turkey has been attempting in recent months to impose a suffocating framework, in this case for the Great Sea Interconnector (GSI), the electricity connection between Crete and Cyprus, making the following unfounded claims:
Ankara insists on requiring information in order to then choose whether to authorize the exploration ships that are surveying the relevant area at the bottom of the continental shelf for the laying of the Cyprus-Greece electrical interconnection cable. It raises this requirement not only by citing the illegally delimited Turkish-Libya continental shelf, which overlaps the legal Greek-Egyptian one, but also with regard to areas of the continental shelf that have not been delimited. In the first case, in August 2024, south of the island of Kasos, Turkey prevented the exploration vessel by deploying warships. In the second, north of Crete in February 2025, Ankara also demanded permission.
In the Kasos incident, Ankara urgently requested to be informed to verify the feasibility of the exploration and to give its approval. This is a standard procedure for Turkey which Greece has never protested against. The laying of a cable and the preliminary surveying constitute freedom of the high seas – Article 79 of the Law of the Sea Convention (1982), which is binding as customary law. In the Kasos incident, Greece reacted, not on the basis of the article on the freedom to lay submarine cables and pipelines, but with the argument that the exploration was taking place on the continental shelf-exclusive economic zone (EEZ) delimited with Egypt. This position creates a negative precedent, is not based on a correct, for our interests, interpretation of the law of the sea, and therefore carries the risk that in a subsequent phase it will not be possible to continue the project without the obligation to inform Turkey. It must be made clear that we have an unshakable argument, which is the principle of freedom of the high seas, which ensures unhindered research and cable laying on the continental shelf.
It is noted that the Greek authorities also request information and issue permits (Committee for Granting Marine Research Permits) for similar actions by third parties in the seas within the limits of Greek claims to the continental shelf and EEZ, as those claims are formulated in the so-called Maniatis law of 2011.
In the second case in February 2025, when a Turkish corvette shadowed a Greek-leased research vessel north of Crete, Turkey again insisted, in addition to being informed, that any surveying must have its approval. At the same time, it reiterated that it claims the continental shelf east of the 25th meridian in the Aegean. However, this is an non-delimited/disputed area of the continental shelf, which Greece reasonably claims as the exclusive claimant. And because this concerns the Aegean, Turkey additionally accuses Greece of not respecting the 1976 Bern Protocol. That is, it reinstates the obligation that the two countries have undertaken to refrain from initiatives or actions on the Aegean continental shelf that will cause problems or hinder negotiations, as they were conducted in the second half of the 1970s. The Bern Protocol that Turkey invokes only concerns abstention from exclusive exploration of the continental shelf and not exploration for laying a cable.
The laying of a cable and the exploration for that purpose undoubtedly constitute freedom of the high seas, as expressly guaranteed in Article 79, paragraphs 1 and 2, of the convention. The laying of a cable may not be prevented on the continental shelf, provided that due regard is given to not interfere with or affect the sovereign rights of the coastal state to explore the continental shelf and exploit hydrocarbons. Sovereign rights take priority over the freedoms of the sea. Account must also be taken of cables already laid in the same area.
Even if the coastal state takes reasonable measures for the exploration and exploitation of hydrocarbons, the laying of the cable – and consequently the surveying – may not be prevented. And conversely, when the coastal state exercises sovereign rights over the continental shelf, it must take due account of the freedoms of the high seas, such as the laying of a cable. In this way, the rights of both sides, the coastal state and the third state, are exercised in a balanced manner. This clause does not imply permission or consent for the free laying of the cable, which is not affected or interferes with the delimited or non-delimited continental shelf.
The response to studies by Turkish colleagues who attempt to justify why Turkey’s approval and permission should be sought even for research linked to laying a cable – since in their view it may also involve activity that refers to the status of the continental shelf – is the following: the Convention on the Law of the Sea does not confuse (on the contrary, it distinguishes between) the two types of exploration. Surveying and laying a cable and the infrastructure for this do not bring about changes in the physical state of the seabed, nor are the cables differentiated from each other. The cable in question will transmit electrical energy, but even if it were to transmit data, it would not change the freedom of laying. Nor is it a cable that will collect seismic data, because for this information scientists use sonar. Turkey is artfully attempting to include in special purpose rights – and potentially on a non-demarcated continental shelf – the right to free exploration inherent in laying a cable, in order to exercise control over the area.
If free surveying is not disentangled from the continental shelf, the collateral consequences will multiply. It is now obvious that Turkish demands are making it difficult to implement the project for an underwater cable, the laying of which risks being frozen already at the surveying stage. The Greek side, in addition to greater doses of determination, must redefine its tactical and strategic approach to this issue.
At a historical turning point, where the resilience of Europe is being tested and the protection of all kinds of European infrastructure and networks from hybrid attacks by malicious third parties has become a necessary condition, the EU must equally raise its stature and provide its clear support to all projects that not only consolidate its presence in areas of intense interest, such as the Eastern Mediterranean, but also contribute to its much-desired security of energy supply.
Petros Liakouras is a professor of international law and director of the International and European Studies postgraduate program at the University of Piraeus, and Constantinos Filis is an associate professor at the American College of Greece and director of its Institute of Global Affairs.