Turkey is warning that it views the arrival of Greek soldiers to the island of Kastellorizo as a violation of the 1947 peace treaty, and is urging them to demilitarize the island. Greece is seeking to extend its maritime sovereignty to the waters around it.
That’s a big problem for Turkey, because Kastellorizo is just off the Turkish coast, and expanding sovereignty there would severely limit Turkey’s own coastal waters nearby. This becomes an even bigger issue when one considers the UN law of the sea convention.
The area is plainly the coast of Turkey, but Greece has argued that the continental shelf should include its islands, which would give them an exclusive zone of use there, and take it away from Turkey.
Turkey has been increasingly interested in offshore development, and has been securing deals with nations like Libya to explore for oil and gas. Since their claims run upĀ against Greek claims, this is a potential source of tension, and nowhere is it more plain that Kastellorizo.