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Charging for or threatening safe passage would amount to extortion:
Under international law, Iran does not have unilateral legal control to close the Strait of Hormuz. While Iran and Oman share territorial waters within the strait, they are bound by the international law of transit passage, which guarantees innocent passage for ships and prevents arbitrary closure.
Key Legal Constraints:
UNCLOS Standards: The Strait of Hormuz is a "strait used for international navigation." The UN Convention on the Law of the Sea (UNCLOS) allows coastal nations (Iran and Oman) to pass rules for safety but not to stop or restrict transit.
Transit Passage Rights: All ships and aircraft, including military vessels, have the right of "continuous and expeditious" passage that cannot be suspended by Iran.
Customary International Law: Even though Iran is not a party to UNCLOS, the rules of transit passage are widely recognized as customary international law, binding on all nations.
Limitations on Action: Iran can only legally act against vessels engaged in illegal activities or "hostile" maneuvers, but it cannot legally declare a total or selective blockade of the strait.