With the announcement made this Sunday by the president of the United States, Donald Trump, to impose a perimeter closure on the Strait of Hormuz —already under Iran's control since the start of the war with the United States and Israel on February 28—, this key route for international trade, especially energy, through which approximately one-fifth of the oil and liquefied natural gas that moves by sea on the planet circulated, has been de facto closed to commercial navigation.
Trump has hardened his stance on the strait after the failure this Saturday of high-level peace talks between the United States and Iran, held in Islamabad, capital of Pakistan. In a forceful message disseminated on social media, he has held Tehran responsible for this decision and has also warned that the US Navy will intercept any merchant vessel suspected of having paid the "toll" that Iran demands since it took control of the passage.
According to Trump, this interception will take place "in international waters"; a formulation that further complicates the scenario, given that Washington is not part of one of the main agreements that define this concept, the United Nations Convention on the Law of the Sea, which establishes that every State can establish its territorial sea up to a maximum of 12 nautical miles.
A legal labyrinth around the strait
The Strait of Hormuz reaches a maximum width of 21 nautical miles. Iran and Oman each claimed their 12 miles of territorial sea in accordance with the convention in 1959 and 1972, respectively. Tehran, until it decided to assume effective control of the passage, had applied these rules selectively.
The United States, for its part, has presented itself for years as a firm champion of "freedom of navigation" and, when it resorts to the convention, it does so as "customary international law," that is, as a set of practices so widespread that they are considered obligatory even without formal adherence, as recalled by the NGO Better World Campaign, based in Washington D.C, before alluding to the "enormous and complex legal dance" that this crisis entails.
The International Maritime Organization (IMO), through its director, Arsenio Domínguez, has expressed the rejection of the UN body responsible for the safety and security of maritime transport of any formula that involves imposing tolls on the transit of ships through the Strait of Hormuz, since "it would set a dangerous precedent." The European Union has expressed the same position.
Iranian tolls, US blockade and risk for energy trade
Since Iran announced its intention to apply a "toll" to international ships (a measure that in any case excludes those linked to the US and Israel), the Iranian Revolutionary Guard had been recommending "alternative passage routes" which, after Trump's decision, are practically rendered useless. US destroyers and patrol ships can intercept vessels both west of the strait, from Bahrain or Qatar in the Persian Gulf, as well as to the east, between the Gulf of Oman and the Arabian Sea.
Given that Iran will not allow the passage of those ships that do not pay the toll (except for some exceptions for humanitarian cargo) and the US has warned that it will detain those who do pay it, the strait is today, in practice, totally blocked, awaiting to verify in a matter of hours the reaction of international markets and whether Trump decides to launch the promised "mine-clearing operation" to eliminate the alleged Iranian explosive devices in the waters of Hormuz.
This escalation takes place in a fundamental maritime corridor through which, in 2025 alone, some 20 million barrels of crude oil and refined products crossed each day, coming from countries such as Iran, Iraq, Kuwait, Qatar, Saudi Arabia or United Arab Emirates, according to calculations by the U.S. Energy Information Administration (EIA); an energy trade flow valued at around 500 billion euros per year.