The Iranian Threat to Close the Strait of Hormuz: A Violation of International Law?

Abstract

Along with the Strait of Malacca and the Singapore Straits, the Strait of Hormuz is arguably the most important bottleneck in international navigation because a large part of the global oil production needs to be shipped through this passage, which is only a few kilometers wide. In the context of the dispute about Iran’s nuclear program and new sanctions, Iran has threatened to close the Strait of Hormuz for international shipping, effectively cutting off many Western countries from important oil imports. In this article, the legality of such action as well as the legality of the mere threat to close the Strait of Hormuz are investigated. In addition to the International Law of the Sea, general rules of international law and the international law of armed conflict are taken into consideration. Particular emphasis is put on the sovereignty of other states, which is infringed upon by such threats on the part of the Iranian leadership.
First, the question has to be answered whether a passage through these waters would be transit passage through a Strait or normal passage through the coastal state’s territorial sea. The authors of the article conclude that the regime of transit passage applies qua lex specialis, as far as the part of the Strait of Hormuz, which is included in Iran’s territorial waters, is concerned.
The next step is to ask the question whether preventing such a passage as well as threatening to prevent such a passage are permissible for Iran. In this context, the potential abuse of otherwise permitted traffic separation schemes is highlighted. Traffic separation schemes are of particular importance in narrow but highly frequented bodies of water, such as the Strait of Hormuz. In addition, the contemporary Iranian state practice has received some attention. One issue to be considered in more detail is the requirement that foreign warships receive authorization from the coastal state prior to entry into the territorial sea. This approach might be incompatible with the right to innocent passage under both the Law of the Sea Convention and customary international law, as there is no clear legal source, which provides for this requirement.
Finally, the authors look at the question of the legality of the mere threat to close the Strait of Hormuz as opposed to actually closing the Strait. The sovereignty of other states may be affected to such an extent that such threats already amount to a violation of international law. In light of the historic precedents during the Iran-Iraq War, these threats should not be dismissed lightly. Iran would be well advised to refrain from such rhetoric.