Hormuz: Where Law Meets the Gunboat

In the world’s most vital oil chokepoint, the elegant certainties of maritime law dissolve into a murky contest of power, risk and coercion.

The Strait of Hormuz is, in the dry language of international law, a “strait used for international navigation.” In the less sterile vocabulary of geopolitics, it is a loaded gun pointed at the global economy. Barely 21 nautical miles wide at its narrowest point, this corridor connects the oil-rich Persian Gulf to the wider Arabian Sea. Around a fifth of the world’s petroleum flows through it. As the ever-escalating Iran conflict shows, any disruption in Hormuz, whether legal or kinetic, reverberates from Mumbai to Rotterdam.

On paper, the rules governing such a passage are clear enough. The United Nations Convention on the Law of the Sea (UNCLOS) enshrines the principle of ‘transit passage’ for straits like Hormuz by which ships and aircraft, commercial and military alike, may pass continuously and expeditiously without interference. Unlike the more limited concept of ‘innocent passage,’ which coastal states may suspend for security reasons, transit passage is meant to be inalienable. Article 44 of UNCLOS is unequivocal on this count when it states any vessel or craft “shall not be impeded.”

Yet law, as ever at sea, is only half the story. The waters of Hormuz lap against the shores of Iran to the north and Oman to the south. Both exercise sovereignty over their territorial seas. Both insist, at least formally, on adherence to international norms. But sovereignty, especially in a region long shaped by imperial retreat and regional rivalry, has a habit of expanding in moments of crisis.

Legal Regime

The modern legal regime itself is a relatively recent construct. For centuries, strategic waterways were governed less by codified law than by naval power. The British Empire, whose warships once policed the Gulf, ensured freedom of navigation less through treaties than through dominance. When Britain withdrew east of Suez in 1971, the vacuum it left was filled not by a stable multilateral order but by a volatile balance among regional powers, increasingly shadowed by American naval presence.

Since the Iranian Revolution, Hormuz has repeatedly flirted with closure. During the Iran–Iraq War, the so-called ‘Tanker War’ saw both sides target oil shipments, drawing in external powers. American-flagged vessels were escorted through the strait under Operation Earnest Will; mines and missiles rendered legal niceties largely academic. The blunt lesson was that the right of passage exists only insofar as it can be enforced.

UNCLOS, negotiated in calmer waters, is ill-equipped for such moments. It is, fundamentally, a peacetime convention. When conflict intrudes, the legal compass shifts towards customary international law and interpretive guides such as the San Remo Manual on International Law Applicable to Armed Conflicts at Sea. These allow for defensive measures like exclusion zones, interdictions, even blockades, provided they meet stringent conditions. A blockade, for instance, must be declared, effective, and must not indiscriminately harm neutral shipping.

But here the line between legality and expediency blurs. Article 39 of UNCLOS obliges vessels in transit to refrain from any threat or use of force. Yet what constitutes a ‘threat’ in a militarised strait? Is a swarm of fast attack craft shadowing a tanker an act of intimidation or a legitimate security patrol? When drones hover and warships loiter, the distinction becomes as narrow as the channel itself.

Grey-Zone Tactics

In practice, states have developed a repertoire of what might be called ‘grey-zone’ tactics. Rather than formally suspending transit passage, which would be a clear breach of international law, they impose de facto constraints. Naval exercises are announced in sensitive lanes. Radio warnings proliferate. Tankers are boarded or briefly detained on ostensibly technical grounds. Each action falls short of outright obstruction.

For the global shipping industry, this ambiguity is a mounting cost. Insurance premiums spike at the first hint of tension. War-risk clauses are invoked. Shipowners reroute vessels, sometimes at considerable expense, to avoid perceived hotspots. Crews, often drawn from poorer countries, bear the psychological burden of navigating waters where the rules are both rigid and malleable.

The result is that while UNCLOS promises a frictionless corridor for global commerce on paper, operational reality delivers something closer to a negotiated passage, contingent on the shifting calculations of coastal states and external powers. In effect, risk is outsourced from governments that contest the strait’s status to the private actors who must traverse it.

Nor is this tension likely to dissipate. As energy markets evolve, Hormuz remains indispensable. Even as the world talks of transition, hydrocarbons still flow overwhelmingly through this narrow artery. Meanwhile, regional rivalries endure, and the presence of extra-regional navies ensures that any local incident risks broader escalation.

What, then, is to be done? Calls for stricter enforcement of international law are well-intentioned but insufficient. Law, in the maritime domain, has always depended on a convergence of interests among major powers. Where such convergence is absent, as it often is in the Gulf, legal norms become aspirational.

While Iran and Oman may regulate navigation for safety and security, the situation highlights an enduring tension between international legal norms and strategic realities. It underscores the need for global maritime governance to evolve, addressing not only compliance in stable conditions but also resilience in conflict environments.

(Capt. Singhal is a shipping and marine consultant and member, Singapore Shipping Association. Capt. Saggi is ex-Nautical Advisor to Government of India. Views personal.)