A Turning Point: From Diplomacy to Confrontation Following the failure of the Islamic Republic of Iran to reopen the Strait of Hormuz – set as a precondition for negotiations in Islamabad – the President of the United States announced that the United States would impose a blockade on the Strait. This sequence of events shifts the situation from diplomatic deadlock to legal confrontation. The central question is no longer simply political: what are the legal consequences of Iran’s conduct, and what, in turn, can the United States realistically achieve through a blockade under international law?

Why the Strait of Hormuz Matters The Strait of Hormuz is not merely a regional passage. It is one of the world’s most critical maritime chokepoints, connecting the Persian Gulf to the open ocean and carrying a substantial portion of global energy supplies. Its legal status is therefore not incidental. Under the United Nations Convention on the Law of the Sea (UNCLOS), it qualifies as a strait used for international navigation and is governed by a specialized regime that limits the discretion of coastal states in favor of global transit rights.

These rules are widely regarded as reflective of customary international law, meaning they bind states irrespective of formal treaty ratification. Their purpose is structural: to ensure that key maritime arteries remain open, predictable, and secure. The Strait of Hormuz is precisely the type of waterway these rules were designed to protect. Any erosion of this regime risks undermining not only regional stability but also the broader system of global maritime governance.

The Legal Framework: Transit Passage and State Obligations Two provisions of UNCLOS are particularly relevant, and their implications are more far-reaching than often appreciated. Article 38 establishes the right of transit passage, which differs fundamentally from the more limited concept of innocent passage applicable in territorial seas. Transit passage cannot be suspended and may not be regulated in a manner that has the practical effect of denying or impairing transit passage. It guarantees continuous and expeditious navigation and overflight for all vessels and aircraft, including military ones, so long as they proceed without delay and refrain from activities not incidental to transit. In practical terms, this means that Iran cannot lawfully close the Strait, selectively deny access, or impose conditions that would undermine the free flow of maritime traffic.

Article 44 reinforces this framework by imposing affirmative obligations on states bordering international straits. It does not merely prohibit obstruction; it requires that such states “shall not hamper transit passage” and must give appropriate publicity to any dangers to navigation. This creates a dual duty: a negative obligation not to interfere, and a positive obligation to ensure safety. The legal threshold is therefore not limited to intentional closure. Even indirect interference – such as failing to remove hazards, neglecting to warn of known risks, or allowing unsafe conditions to persist – can constitute a breach where such omissions amount to a failure of due diligence and result in hampering transit passage.

Iran’s Position Under International Law Applied to the current situation, these provisions place Iran in a legally exposed position. The reported presence of naval mines in the Strait, combined with the assertion that their locations may be unknown, is difficult to reconcile with either Article 38 or Article 44. Mines that are not properly tracked and disclosed do not merely create a theoretical risk; they materially impede the ability of vessels to exercise their right of transit passage. The obligation to give “appropriate publicity” to dangers entails a duty of due diligence: coastal states must take reasonable steps to be aware of hazards within their waters and to communicate known risks to mariners. Where a state has deployed mines or is aware (or ought reasonably to be aware) of their presence, a failure to provide adequate warning or to manage the resulting risk may constitute a breach of its obligation not to hamper transit passage.

What the Courts Have Already Said Judicial precedent reinforces these obligations. In the Corfu Channel case, the International Court of Justice held Albania responsible for failing to warn of mines in waters used for international navigation. The Court did not require proof that Albania had laid the mines itself; rather, responsibility was based on the finding that it knew, or ought to have known, of their presence and failed to act. From this, the Court articulated a broader principle of due diligence: a state must not knowingly allow its territory to be used in a manner that causes harm to other states.

The legal consequences of such responsibility are reflected in the Articles on Responsibility of States for Internationally Wrongful Acts and include cessation of the wrongful conduct, assurances of non-repetition, and full reparation for injury caused. In this context, that may require disclosure of mine locations, compensation for damage, and the adoption of measures necessary to eliminate or mitigate the hazard. Where a state fails to comply, other states may invoke responsibility and adopt proportionate countermeasures consistent with international law. Any further steps taken to protect navigation must remain within the limits imposed by the law on the use of force and other applicable rules of international law.

When Law Meets Practice: Immediate Consequences The legal........

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