Caspian Sea’s Shared Legal Regime Leaves No Fixed National Ownership

For decades Iran argued over how much of the Caspian Sea it should control, citing historic bilateral treaties with the Soviet Union that emphasized shared use rather than ownership. After the Soviet collapse, the newly independent Azerbaijan, Kazakhstan and Turkmenistan turned the dispute into a five-nation negotiation. The 2018 Convention on the Legal Status of the Caspian Sea, signed in Aktau, established up to 15 nautical miles of territorial waters and a 10-nautical-mile exclusive fishing zone for each bordering state, while keeping the remaining surface open to all.

It also prohibits armed forces of non-littoral states from operating in the basin, a rule highlighted by Iran’s accusation that Ukraine attacked an Iranian commercial vessel. Although the treaty creates a special legal framework, it does not allocate fixed percentages of the water or seabed, leaving Iran’s offshore hydrocarbon claims subject to future bilateral delimitation. Iran’s most promising Caspian field, Sardar-e Jangal, lies in deep water and faces technical and sanction-related hurdles, prompting the country to favor development of its Persian Gulf resources instead.