In April 2025, Greece announced its first marine spatial planning (MSP), accompanied by an official map which divides the Ionian and the Aegean Seas into four different spatial units (See here for the official announcement in Greek – The map is further provided and explained below). While MSP in Greece had been under discussion for years, prompted by Greece’s obligations under EU Directive 2014/89/EU, this announcement marks the first time Greece has officially mapped the entirety of its maritime claims. While MSP is primarily a domestic tool for environmental coordination and resource management, its adoption in a legally contested maritime space necessarily raises issues of international law and the law of the sea.
This post explores the legal relevance of Greece’s MSP from the perspective of international law. First, it introduces the concept of MSP and the context of its publication. Second, it analyses the evidentiary function of maps in boundary disputes, focusing on how such instruments can contribute to the stabilisation of legal claims. Finally, it considers the role of MSP within the framework of UNCLOS obligations in undelimited maritime zones. This post suggests that, irrespective of broader geopolitical narratives, such regulatory acts may support (rather than hinder) the eventual process of maritime delimitation by clarifying States’ positions and fostering dialogue.
Understanding MSP – The Example of Greece
MSP is typically a domestic regulatory tool, designed to regulate and coordinate the potential clash between different uses of a maritime space. Specifically, under EU law, Member States are required to develop MSPs, taking into account numerous criteria relating to activities and uses of the ocean (Articles 4 and 6, EU Directive 2014/89/EU). Thus, Greece’s announcement is part of a broader European obligation in an attempt to promote “[…] the sustainable growth of maritime economies, the sustainable development of marine areas and the sustainable use of marine resources” (Article 1, EU Directive 2014/89/EU).
Nevertheless, MSP presumes a certain level of certainty over the maritime zones it regulates. In many EU contexts -such as France’s and Denmark’s maritime plans- this assumption is valid because maritime boundaries have been agreed upon. In contrast, Greece’s maritime zones remain partially undelimited. While some zones are clearly defined, large parts of the Aegean and Eastern Mediterranean remain unresolved due to the absence of delimitation agreements, particularly with Türkiye.
The official map published by Greece illustrates these positions. To ease the understanding for non-Greek speakers, the map reflects: a 12nm territorial sea in the Ionian Sea; a 6nm territorial sea in the Aegean Sea (reserving its right to extend it to 12nm); and Greece’s EEZ agreements with Egypt and Italy (the latter pending into force). While these negotiated agreements are reflected in the map, what is absent are pending maritime boundaries with other States. In these areas, the map adopts a median line reflecting Greece’s interpretation of the extent of its continental shelf, including that of its islands, which are accorded full effect under its legal view. In this way, the MSP may also serve to articulate Greece’s legal interpretation of its maritime entitlements.
Mapping Claims Through MSP
Although maps alone do not create legal entitlements, they can function as evidence of State conduct or intention. Already since the 1986 Burkina Faso v. Mali case, the ICJ perceives maps as “only illustrative”, unless, for example, explicitly incorporated into agreements (Judgment, para. 54). Yet maps can help formalise maritime claims, particularly when they are consistent with other State practice.
Whether a State’s claims have been formalised is relevant in delimitation proceedings, as international courts and tribunals often consider the clarity and consistency of a State’s position when assessing competing claims. For instance, in Nicaragua v. Colombia, the ICJ acknowledged that while maps have limited evidentiary value for title, they may nonetheless support a State’s position if used consistently (Judgment, paras 100-102). Though the case addressed sovereignty over islands, the rationale can reasonably extend to maritime zones.
The critical value of maps was further highlighted by the ITLOS in the Ghana v. Côte d’Ivoire case. The Tribunal noted that although maps (as reflected in domestic legislation) are of limited relevance to proving the existence of a tacit maritime boundary (Judgment, para. 163), it also highlighted that the maps to be used during the delimitation process should be “[…] indicative of the Parties’ common confidence in the reliability of these maps […]” (Judgment, para. 342). Thus, maps widely used by States to illustrate their maritime positions play a crucial role when it comes to maritime delimitation.
In this context, Greece’s MSP map may reflect a shift from evolving practice to a more formal and transparent articulation of maritime jurisdiction. This transparency could be legally relevant in the Eastern Mediterranean, where overlapping claims persist. If consistently applied, the MSP could serve as part of the evidentiary landscape in future dispute resolution mechanisms.
Türkiye’s Response: Legal Contestation and Regional Signalling
Türkiye swiftly reacted to Greece’s MSP, claiming that the plan violated its maritime jurisdiction in the Aegean and Eastern Mediterranean (Press Release No. 84). It asserted that these “unilateral actions” have no legal consequences for Türkiye and reiterated the principle of cooperation in semi-enclosed seas (Press Release No. 84).
The statement also referenced the Athens Declaration on Friendly Relations and Good Neighbourliness (7 December 2023), framing its position in terms of a broader commitment to dialogue. While expressing strong objections to Greece’s plan, Türkiye express its wish “[…] to resolve issues on the basis of international law […]” (Press Release No. 84). Finally, it is stated that Türkiye will submit its own MSP. In the past, Türkiye has issued several maps reflecting its positions with respect to maritime zones in the Aegean and the Mediterranean Sea (see the most recent here). Accordingly, a Turkish MSP would likely reflect its own legal interpretations, continuing a trend by both States to use regulatory instruments to communicate jurisdictional positions.
While brief, Türkiye’s reaction underscores the legal importance of a timely objection. As the ICJ observed in the Temple of Preah Vihear case, silence or failure to contest maps may be interpreted as acquiescence (Judgment, p. 32). Thus, contesting Greece’s MSP is not simply a political statement but rather a legal act aimed at preserving Türkiye’s claims.
Legal Implications in Undelimited Maritime Areas
While nothing prohibits States from announcing their MSP in areas of contested jurisdiction, the MSP must also be considered within the framework of Articles 74(3) and 83(3) UNCLOS. These provisions require States with overlapping maritime claims to enter into provisional arrangements and avoid actions that may jeopardise final delimitation.
Provisional arrangements are “[…] designed to promote interim regimes and practical measures that could pave the way for provisional utilisation of disputed areas pending delimitation” (Guyana v. Suriname, Award, para. 460). Although no specific form is prescribed, it can range from agreements to non-binding documents (Churchill, p. 149). What is, however, implied -considering also the wording of Arts 74(3) and 83(3) UNCLOS- is that these arrangements have to be at least bilateral. Thus, while unilateral MSPs do not qualify as such arrangements, they may serve a preparatory role. Once the relevant activities that require regulation are mapped, States might more easily proceed to the conclusion of “provisional arrangements of a practical nature”.
When it comes to the obligation not to jeopardise or hamper the reaching of the final agreement, the Guyana v. Suriname Arbitration provides, once again, useful guidance. There, the Arbitral Tribunal differentiated between activities causing permanent physical change (e.g., drilling) and those that do not (e.g. seismic exploitation) (Award, para. 467). What is, therefore, required is a specific ‘physical’ activity. MSP, as a mere regulatory framework that outlines zoning priorities within specific maritime areas, would not typically be considered as breaching this obligation.
Concluding: The Subtle Role of MSP in Disputed Waters
The emergence of MSP as a tool of legal expression in the law of the sea seems to present new questions for international law. Greece’s recent plan -and the map embedded within it- raises the question of how such domestic regulatory acts can intersect with international law. From the analysis above, it is clear that acts of spatial planning should not be seen as purely domestic matters. As maritime disputes evolve, such regulatory instruments can serve as vehicles through which States clarify, stabilise, and try to assert their legal positions. However, the deployment of such strategies is not unique to legally well-founded claims and may equally be used to support expansive or contested positions. While MSPs do not establish legal rights or replace boundary agreements, their role in shaping the narrative of maritime claims can be proven increasingly significant. In this light, the value of MSP in disputed maritime areas lies not in its capacity to settle claims, but in its ability to clarify them. It reflects how States translate legal argument into spatial governance, fostering dialogue in complex maritime regions.