Carving Up Ukraine: What About the Azov Sea?

Among other things, the ongoing negotiations to end hostilities in the Russia-Ukraine War include a maritime ceasefire agreement for halting hostilities in the Black Sea. At this stage, no publicly available details exist concerning practice and implementation. Meanwhile, European States are discussing the possibility of sending military forces to Ukraine, with equally unknown parameters.

In this context, the U.S. Special Envoy for Ukraine and Russia, General (ret.) Keith Kellogg, suggested dividing Ukraine into areas of responsibility for the deployment of such a force. As some media outlets have noted, the force would also encourage trade in the Black Sea, implying a naval presence. According to one report, U.S. President Donald Trump suggested Ukraine should give up Crimea as a step toward peace.

While some maps show possible divisions of the territory into spheres of control or division, one part of Ukraine’s territory remains unnoticed (or at least unmentioned): the Sea of Azov. In its entirety, this sea roughly equals the size of two occupied provinces. It also provides access to and from the Caspian Sea and has several ports, making it a strategically important maritime area.

If coalition forces send a naval presence to the region that includes the Sea of Azov as an area of operation, at least two intertwined legal issues will emerge: 1) who owns the Sea of Azov; and 2) what status does it have? This short post will offer a brief analysis of these issues.

The Sea of Azov

Since Ukraine’s independence in 1991, both Russia and Ukraine have bordered the Sea of Azov. In 2003, Russia and Ukraine concluded a bilateral agreement on cooperation on the use of the Sea and the Strait of Kerch (2003 Treaty). After the Russian occupation of Crimea in 2014, the Kerch Strait came under Russia’s de facto control. Russia then built a bridge over the Strait, limiting the size of the shipping deliverable through it.

In 2016, Ukraine filed a claim against Russia before an arbitral tribunal constituted under Annex VII of the UN Convention on the Law of the Sea (UNCLOS) (Concerning Coastal State Rights in the Black Sea, Sea of Azov, and Kerch Strait) to protect Ukraine’s rights over the Black Sea, the Sea of Azov, and the Kerch Strait. In November 2018, three Ukrainian naval vessels attempting to pass the Kerch Strait were caught in hostilities with Russia, prompting the International Tribunal on the Law of the Sea to examine the situation. At the start of renewed hostilities in February 2022, Russia suspended navigation in the Sea of Azov. Today, Russia occupies the land territory encircling the Sea of Azov and has complete control over the Azov Sea.

Legal Positions on the Sea of Azov

Russia and Ukraine take different views on the legal status of the waters in the Sea of Azov. Russia’s view holds that the Sea of Azov historically falls under internal waters, a position clearly stemming from the proceedings in the ongoing UNCLOS Annex VII litigation. This view, under which Russia claims historical title dating to the Russian Empire and through the Soviet era, also found its way into Article 1 of the 2003 Treaty. Article 1 provides, “The Sea of Azov and the Kerch Strait are historically internal waters of the Russian Federation and Ukraine.”

Both the view that Russia claims historical title—an issue on which UNCLOS is silent—and the view that this sea is internal waters—an area which according to Russia is outside the scope of UNCLOS—are reasons for Russia not to apply UNCLOS. While Russia accepts it must share the Azov Sea with Ukraine per the 2003 Treaty, Russia has nonetheless argued the Sea constitutes pluri-State historically internal waters. Article 1 of the 2003 Treaty also mentions that the State borderline will be delimited in accordance with an agreement between the parties. No such agreement appears to exist, however.

Ukraine’s position, also expressed in the opening statement of the hearings of the UNCLOS Annex VII Tribunal in September 2024, insists that UNCLOS applies. According to Ukraine, since the dissolution of the Soviet Union, the Azov Sea no longer qualifies as internal waters. It is instead a semi-enclosed sea that should have territorial seas and exclusive economic zones (EEZ). Consequently, the Kerch Strait, which gives access to the Sea, must be considered as an international strait. In Ukraine’s view, the Strait connects the EEZs of the Sea of Azov and the Black Sea and is used for international navigation. Therefore, the navigational right of transit passage applies, which allows vessels to pass under the conditions of that regime.

Ukraine’s view backpaddles on the 2003 Treaty, but both Ukraine and Russia appear to have denounced this treaty. In Russia’s view, the Eastern Provinces and Crimea are already acceded to Russia so that the sea and “their coasts belong to the Russian Federation alone.” Russia has purportedly also initiated national legislation defining the whole Azov Sea as Russia’s internal waters.

Land Dominates the Sea

Apart from different positions on its legal status, since Russia’s full-scale invasion in February 2022, Ukraine’s entitlements over its part of the Sea of Azov have come under increased pressure. As a principle, maritime rights over the sea come from a State’s sovereign rights over its land territory. The principle of “land dominates the sea,” as famously described in 1969 by the International Court of Justice in the North Sea Continental Shelf cases (para. 96), holds that determining maritime claims starts with territorial analysis. In this context, a complete loss of Ukraine’s coastal areas bordering the Sea of Azov could result in a loss of Ukraine’s maritime claims over the Sea of Azov, arguably putting Russia in a more favourable position to bolster its view on the legal status of the Sea itself.

Others have already written on the legality of a treaty between Russia and Ukraine in relation to the law of territorial acquisition as a result of war. In this context, Professor Michael Schmitt has argued the prohibition of territorial acquisition also applies if a transfer of territory is part of a treaty secured in violation of the use of force prohibition. Extending the issue into the maritime dimension, a related question is whether any agreement will have consequences for the claims over maritime areas connected to the coastal areas. Arguably, any agreement short of an actual peace agreement will not have a direct effect on this question, because it will not finalize the land dispute. But it will perhaps tip the Sea towards greater de facto control by Russia.

Sea Control and Navigation for Foreign Warships

With these two intertwined legal issues—who owns the Sea of Azov, and its legal status—in mind, and turning towards possible navigational consequences following any decision to deploy a coalition naval force into the region, one can easily see the differences and consequences of both positions. In short, where Ukraine’s position allows for navigational freedoms for third States through the Strait and in the Sea of Azov, Russia’s position nullifies those navigational rights under international law and brings navigation of and into the Sea wholly under State permission.

Leaving aside the Montreux issue currently barring access for foreign navies into the Black Sea through the Turkish Straits, if a coalition naval force saw an operational need to deploy to the Sea of Azov, how would participating States treat the Kerch Strait legally and the navigational regime in the Azov Sea? In a 2018 statement disapproving of the construction of the bridge over the Kerch Strait, the European Union made only a faint reference to UNCLOS providing freedom of navigation, expressing nothing in the way of a legal view over the area. From a scholarly perspective, authors appear reluctant to reach clear conclusions on the legal status of the Sea since 1991 (on this point, Schatz and Koval provide an outstanding and detailed analysis).

Russia has already expressed that it does not accept any British military assets in the Sea of Azov. Whether there is an actual need to deploy into the Sea of Azov depends on the architecture of the mandate and the ends, ways, and means to fulfil the given mandate. But in any event, this legal minefield poses challenges for deployment that could, even at the planning stage, exclude deploying forces in the area at all.

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Captain Martin Fink is a legal advisor in the Royal Netherlands Navy and research fellow at the Royal Netherland Defence Academy. He currently holds the position of Head of Legal Affairs of the Royal Marechaussee.

The views expressed are those of the author, and do not necessarily reflect the official position of the United States Military Academy, Department of the Army, or Department of Defense. 

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Photo credit: MODIS Land Rapid Response Team, NASA GSFC