Wissem Seddik is a doctor in public law. He prepared his thesis under the direction of Pr. Marie-Pierre Lanfranchi, in the DICE-CERIC of Aix-Marseille University. This thesis, entitled “Maritime planning in the Mediterranean. A study on the contribution of a public policy instrument to the implementation of the international law of the sea”, was defended in June 2025.

On April 16, 2025, Greece launched a national strategy outlining and mapping its maritime spatial planning (MSP). As the result of intensive work involving various ministries, local authorities, and non-governmental actors, this strategy provides a comprehensive framework for managing marine space by conciliating the development of the maritime economy with environmental protection. This MSP was the subject of an article written by Mr. Dimitris Panousos, published in the European Journal of International Law’s blog (EJIL Talk!), and analyzing the legal consequences of this current event on the maritime dispute between Greece and Turkey, particularly in the Aegean Sea. This article is, for the most part, a response to the previous piece, extending some of its analyses.

The MSP as support for national claims to a disputed maritime zone

The emergence of MSP in the Aegean Sea marks a new chapter in the long history of this dispute – whose roots date back to Homeric times. While the dispute extends across the eastern Mediterranean, it is prominent in the Aegean, where it has become a real legal headache, as several disagreements have combined to increase the complexity of the situation, namely: the width of the territorial sea, the delimitation of the continental shelf, and the regime of islands.

It is undoubtedly with this dispute in mind that the Greek authorities emphasized, when publishing their MSP map, that its geographical scope had been determined in accordance with international law under the United Nations Convention on the Law of the Sea (UNCLOS). Indeed, the Greek map illustrates a position that gives full effect to island coasts as a baseline for determining delimitation in accordance with the island regime set out in Article 121 of the Convention. However, given that almost all the Aegean islands are Greek, this approach results in incorporating an overwhelming part of the sea into Greek jurisdiction, thus ensuring its unity up to islands very close to the Turkish shore.

This position is unacceptable to Turkey, which defends a solution based on the principle of equity, and involving the division of the Aegean Sea along a median line between the continental coasts, ignoring the regime of islands under UNCLOS, which it has not ratified. This approach would virtually enclose the Greek islands located in the Turkish part of the Aegean Sea, thereby fragmenting Greece’s maritime space, which Greece also finds unacceptable.

In response to Greece’s reaffirmation of its position through its EEZ map, Turkey did not merely express its opposition to the zoning shown on the map, stating that its publication is a unilateral action with no legal effect on Turkey. It also published, in June, its own MSP map, reiterating its claims in the Aegean Sea.

Thus, in this disputed maritime zone, MSP seems to entail a reaffirmation of opposite claims. However, according to Mr. Panousos, it may not be solely part of a conflictual approach, but more subtly come about in the prospect of negotiations between the parties with a view to resolving their dispute. The author argues in this respect that the development of MSP in the Aegean Sea involves the dual benefit of clarifying the positions of the parties and encouraging them to engage in dialogue.

The MSP as a possible tool for a negotiation between the parties to the dispute?

Mr. Panousos explains that while maps, as reflecting the position of a State, “is of limited relevance to proving the existence of an agreed maritime boundary”  (ITLOS, Ghana/Côte d’Ivoire, para. 163), they illustrate national claims and can even specify them. In our case, they not only provide a cartographic representation of these claims, but also indicate the uses associated with the claimed area. Through its MSP, each party to the dispute publicly presents its own plan for governing the area, including to the other party, which is the most highly interested. The unilateral expression of national claims is, in a sense, taken to its logical conclusion, as each party can now form a more precise idea of the interests at stake according to the other’s vision. The MSP thus makes it possible to translate the claim relating to maritime jurisdiction into a vision of the uses associated with the marine space, a vision that is itself translated into a governance project.

It is through activities in the disputed area that the confrontation could be defused. Mr. Panousos then puts forward the idea of considering the domestic MSP as a preparatory act for the conclusion of a “provisional arrangement of a practical nature,” as defined in paragraph 3 of Articles 74 (exclusive economic zone) and 83 (continental shelf) of UNCLOS. According to this provision, the States concerned “shall make every effort” to conclude such an arrangement pending the conclusion of a delimitation agreement. The provisional arrangement shall not jeopardize or hamper the reaching of the final agreement and shall be without prejudice to the final delimitation.

A reservation may be noted regarding the assimilation of a national legal act into a preparatory document for an international agreement. To prevent any conflict between legal orders, the act in question should not be binding within the domestic system. In other words, the MSP map published by the national authorities should be legally considered as a draft that is subject to change in the context of international negotiations.

It should also be borne in mind that Turkey, not being a party to UNCLOS, is not bound by the provisional arrangement regime unless its customary nature can be demonstrated, which does not seem clearly established to date (see Y. Tanaka, “Article 74”, in A. Proelß (ed.), The United Nations Convention on the Law of the Sea: A Commentary, Beck, 2017, p. 577). However, the non-ratification of this major text of international law does not preclude the application of some of its provisions. Turkey implicitly refers to this in its statement responding to the publication of the Greek MSP, arguing that international law encourages cooperation between coastal States bordering a closed or semi-closed sea, a formulation reminiscent of Article 123 of UNCLOS. This reference to regional cooperation is not irrelevant to the MSP, which is framed in such a context.

The MSP regional framework as a basis for Greek-Turkish cooperation?

In the Mediterranean, MSP is not only an internal policy instrument for coastal States. It is also approached as a tool for managing marine space at the regional level. As such, it is regulated by the European Union (EU) under Directive 2014/89/EU of July 23, 2014. It is under this framework that the MSP process is being carried out in Greece. Articles 12 (cooperation between Member States) and 13 (cooperation with third countries) of the directive set out the so-called regional sea approach of the European maritime governance strategy.

That said, the application of this directive “shall not influence the delineation and delimitation of maritime boundaries by Member States in accordance with the relevant provisions of UNCLOS” (Article 2, para. 4). In the Greek-Turkish case — a dispute involving a non contracting State to UNCLOS—the EU’s position in favor of using this treaty to delimit maritime boundaries may seem to contradict the principle of neutrality. In recent years, the European institutions, notably through the European Council, have largely tended to support Greece’s position against Turkey’s claims. However, in the Piran Bay case, the EU Court of Justice considered that the applicability of EU law is ancillary to the international settlement of the delimitation (Judgment of January 31, 2020, para. 104). By departing from its usual neutrality on the Greek-Turkish issue, the Union’s legal policy in the Aegean Sea could legitimize the development of the Greek MSP from the EU law perspective, thereby removing the possibility of European mediation to settle the dispute, despite Turkey’s status as a candidate country for EU membership.

The Barcelona system: untapped potential?

MSP is subject to another institutional framework at the regional level, in the context of the Barcelona Convention for the Protection of the Marine Environment and the Coastal Region of the Mediterranean. In 2017, the contracting Parties defined a “Conceptual Framework” for MSP aimed at implementing the Madrid Protocol on Integrated Coastal Zone Management (decision IG.23/7, annex 2; supplemented by 2023 decision IG.26/10).

Although the Barcelona Convention system does not interfere with the rights and claims of States (Article 3, para. 3, of the Convention), its Conceptual Framework for MSP could be used as a guiding framework to reconcile the interests of Greece and Turkey in the relevant matters, based on common theoretical and operational principles. In this case, however, two points mitigate the efficient use of this instrument: first, this regional framework for MSP has a scope limited to the coastal zone which, under the Protocol on Integrated Coastal Zone Management, does not extend beyond the territorial sea of coastal States (Art. 3); second, and most importantly, Turkey has neither ratified nor even signed the Protocol.

Conclusion: perspective of a bilaterally defined planning in the Aegean Sea as a future model

While commonly regarded as a national maritime spatial management tool, MSP is also of interest from an international cooperation perspective, including in the Aegean Sea.

Indeed, the flexibility of zoning induced by planning, through the definition of a graduated range of statuses in terms of uses (priority areas, areas excluding certain activities or, conversely, areas reserved for certain activities) and in terms of regulation’s temporality, can facilitate the joint management of this undefined area. It fosters the establishment of a framework for dialogue to articulate the strategic interests of the parties — rights of passage, issues relating to security and demilitarization, protection of ecosystems, sectoral economic and social interests such as hydrocarbons, traditional fishing, tourism, etc.

Therefore, the MSP could be conceived not only as a preparatory act for the conclusion of a provisional arrangement between Turkey and Greece in the Aegean Sea, but also, beyond that, as the substantive subject matter of such an arrangement. The provisions of Articles 74 and 83 are applicable to the extent that, on the one hand, they are a conventional obligation with regard to Greece and, on the other hand, Ankara adheres to it through the search for a “equitable solution” (paragraph 1 of the above articles). This would lead to the establishment, as a provisional arrangement, of a bilaterally defined MSP, which would probably be less ambitious and more minimalist than a national plan, but also more operational and effective in managing a disputed maritime zone, because it focuses negotiations on agreed uses without preempting the definitive delimitation.

Where divergences may seem unsolvable today, the search for compromise towards a mutually acceptable use of the area is proceeding step by step, on a case-by-case basis. Can MSP pave the way in this direction and give concrete expression to the pragmatism reflected in the Athens Declaration of December 2023? If Athens and Ankara succeed in giving it a structuring role for the joint management of the Aegean Sea, their experience could lay the foundations for an innovative model for resolving territorial disputes.

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