Coastal State are entitled to claim a territorial sea, extending to a maximum of 12 nautical miles (nm) from the baselines of its land territories, be it from mainland territory or a high-tide feature. In the territorial sea, a coastal State has sovereignty, which extends to the air space above it and the seabed and subsoil beneath it.
Greece has not claimed full 12 nm territorial seas from all its mainland territory and islands. This used to be the case in both the Aegean Sea and the Ionian Sea, but Greece recently changed its position with regard to the latter, by making a decree in December 2020, whereby it extended its territorial sea in the Ionian Sea to 12 nm. In the decree, the Greek government also indicated that this approach may be extended to other areas, including the Aegean Sea.
Subsequent news reports have predicted that Greece taking an identical step concerning the Aegean Sea is in the cards. However, can the fact that Greece has changed its position with regard to the Ionian Sea be seen as a sign that a similar expansion of the Greek territorial sea to 12 nm in the Aegean Sea, is looming on the horizon? Answering this question is difficult, but the short answer is ‘not necessarily’. Especially considering the fact that, in the Aegean Sea, the issue of the breadth of the territorial sea has been a highly controversial matter.
The current state of play in the Aegean Sea, as far as the breadth of the territorial sea is concerned, is that Greece still follows the Turkish position to only claim a 6 nm territorial sea from any of its land territories. Greece has, however, never excluded the possibility of it claiming a territorial sea in the Aegean Sea in the future, which extends to a maximum of 12 nm. In fact, Greece has asserted on various occasions that international law entitles Greece to extend its territorial sea to this distance, and that it may take the necessary steps to make this a reality. Viewed in this light, the fact that Greece in its recent decree, whereby it extended the breath of its territorial sea in the Ionian Sea to 12 nm, also indicated to reserve the right to take a similar approach as regards the Aegean sea, is not a novelty, but rather a continuation of a previously and consistently held position.
However, if Greece were to proceed to claim a full 12 nm territorial sea in the Aegean Sea, such a unilateral move will undoubtedly provoke Turkey. Historically, whenever Greece has made any suggestions that it is entitled to a territorial sea of 12 nm in the Aegean Sea, this has been automatically followed by condemnations form Turkey, indicating that it would take whatever steps necessary to prevent Greece from making such an extension. In fact, Turkey has regarded Greece extending its territorial sea within the Aegean Sea beyond 6 nm as a casus belli. Turkey also takes the position that to claim full territorial sea entitlements within the geographical context of the Aegean Sea, which is rather congested, amounts to an abuse of rights by Greece, as it would lead to Turkey being inequitably affected by such an extension.
One aspect that may explain Turkey’s opposition to such an extension is that this would place approximately two third of the Aegean Sea under the sovereignty of Greece. There is also the issue of that Turkey never acceded to the 1982 Law of the Sea Convention, whereas Greece ratified the Convention in June 1995. This means that Turkey may not be directly bound by its Article 3, which deals with the breadth of the territorial sea, unless the provision therein reflects a customary rule. In this vein, the International Court of Justice in Territorial and Maritime Dispute (Nicaragua v. Columbia) made it clear that Article 3, and the breath of the territorial sea of 12 nm set out therein, have indeed evolved into a customary rule (para. 177, p. 690). There is a caveat, however: if Turkey would be able to demonstrate consistently objecting to this being a customary rule, at the time that it was in the process of obtaining such status, Turkey would not be bound by it once the rule obtains customary status. A potential difficulty in this regard is that Turkey itself claims 12 nm territorial seas in both the Black Sea and the Mediterranean Sea.
Whether Greece will claim a full 12 nm territorial sea in the Aegean Sea as well remains to be seen. However, due to the fundamentally different dynamics that are at play in the Aegean Sea, including its more complex geography, volatility, and the long history of conflict that exists between Greece and Turkey in relation to this area, an expansion of the Greek territorial sea to 12 nm there is perhaps not to be expected soon. Although Greece may have international law on its side on this point, this would increase and lead to further conflict with Turkey.