The legal framework for the Strait of Hormuz is the United Nations Convention on the Law of the Sea (UNCLOS). Article 38 grants all ships and aircraft the right of transit passage through straits used for international navigation. Coastal states, including Iran, cannot suspend or deny this right. UNCLOS allows exceptions only for safety or environmental protection. Political or discriminatory motives are not valid grounds.
An unlawful denial occurs when a state blocks passage, threatens force, or imposes conditions based on nationality. Declaring a ban on U.S. vessels would violate Article 38 and Article 45. Such a ban must be formally enacted and enforced to count as a legal prohibition.
Iran has not issued a formal legal ban on U.S. vessels through the strait. It has made threats and conducted provocative military actions. These include seizing vessels and harassing ships. These acts do not create a legally recognized ban under UNCLOS. A formal, publicly promulgated rule targeting U.S. vessels would be required.
Threatening to block passage is a political or military posture. It does not constitute a legal blockade. A blockade requires effective physical closure enforced by military means. It also requires formal notification and application to all vessels, not just some. Iran’s actions have not reached this threshold.
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