Opinion | Why blocking the Strait of Hormuz is a recipe for disaster
With its ruinous consequences and difficulty in execution, a full blockade is unlikely. But the risks of miscalculation must not be ignored
With commercial vessels reportedly beginning to divert, the critical question is not just whether Iran can disrupt traffic, but whether it will implement a complete blockade. A careful examination of the legal framework, strategic considerations and economic realities suggests that, although the risk of miscalculation is high, a sustained closure of the strait remains an unlikely and counterproductive option for Tehran.
From the perspective of international law, Iran’s hands are largely tied. In principle, the Strait of Hormuz should be governed by the UN Convention on the Law of the Sea (Unclos). This convention establishes the right of “transit passage”, which guarantees all ships and aircraft continuous and expeditious passage. Crucially, Unclos states this right “shall not be impeded” or suspended by coastal states.
While Iran has signed but not ratified Unclos, the transit passage regime is accepted as customary international law, binding on all nations. Even under the Convention on the Territorial Sea and the Contiguous Zone, one of four treaties agreed on at the first UN Conference on the Law of the Sea in 1958, straits used for international navigation are subject to a non-suspendable right of innocent passage.
Tehran may attempt to justify a blockade under Article 51 of the UN Charter, claiming self-defence in response to the air strikes. However, this argument is unlikely to withstand legal scrutiny. The principles of necessity and proportionality are central to the right of self-defence.
A blanket closure of the strait would inflict disproportionate harm on neutral third countries, including energy-hungry economies in Asia and Europe – arguably making it an illegal act of collective punishment as opposed to a legitimate act of self-defence. According to international humanitarian law, self-defence measures must not unduly harm third parties.
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