Since autumn 2011, the United States, United Kingdom, and France have boosted their military presence in the Gulf. In January 2012, the USS Abraham Lincoln, a U.S. aircraft carrier, was sent through the Strait to conduct “maritime security operations,” accompanied by a British warship and a French vessel. According to a statement by the U.K. Ministry of Defense, the move was made “to underline the unwavering international commitment to maintaining rights of passage under international law.” U.S. Secretary of Defense Leon Panetta recently added in February 2012: “If we have to deal with someone trying to close the Straits of Hormuz, we have the naval and air force capability to be able to do that. We can do that in conjunction with NATO, or we can do it on our own.”
Despite heated press statements, the U.S. administration and the Iranian leadership are aware of the legal arguments for, or against, a possible closure of the Strait of Hormuz. The International Law of the Sea is unambiguous on the matter. It requires maritime straits to remain open. Only in the case of armed conflict, Iran could be entitled as a belligerent to close parts of the water passage temporarily. A blockade of the Strait of Hormuz in reaction to U.S. and EU sanctions would find some, but not sufficient, legal justification in existing customary international law.