An International-Law Analysis of Iran’s Countermeasure against Greece in Seizing the “Prudent Warrior” and “Delta Poseidon” Oil Tankers

On Tuesday, 19 April 2022, the Greek Coast Guard seized a Russian-owned oil tanker named Pegasus in the waters off the Euboea Island.  It had adopted the Iranian flag and changed its name to Lana just before the Greek action. The seizure of the ship was initially carried out under European Union sanctions against Russia in connection with the attack on Ukraine. However, pursuant to a request by the US Department of Justice - which claimed the tanker’s oil cargo was Iranian and subject to US sanctions- the seizure was continued and a part of the cargo was delivered to the United States. After the seizure of Luna/Pegasus, Iran tried to release the ship through diplomatic and legal measures, but these measures were unsuccessful due to Greece’s refusal. Thereupon, on 27 May, Iran seized two Greek oil tankers in the Persian Gulf called Prudent Warrior and Delta Poseidon. The purpose of this paper is to examine the legality of Iran's seizure of the Greek oil tankers from the point of view of international law, specifically in terms of the law of countermeasures. Using a descriptive-analytical method and collecting information from library and documentary sources, the paper finds that in response to the actions by Greece and the United States, Iran had the right to take countermeasures within the framework of international law, and its seizure and detention of the two Greek tankers did not entail international responsibility.