As tensions rise following U.S. and Israeli strikes across the Middle East, attention has shifted to a narrow stretch of water most Americans rarely think about: the Strait of Hormuz. With gas prices climbing and shipping disrupted, the corridor has become the center of a high-stakes geopolitical and legal question.
Can Iran legally close it?
And perhaps more puzzling, how does a country even close a body of water?
What Is the Strait of Hormuz?
The Strait of Hormuz is a slim maritime corridor between Iran to the north and Oman and the United Arab Emirates to the south. It connects the Persian Gulf to the Arabian Sea and, in practical terms, to global markets.
At its narrowest point, the strait is just 21 nautical miles wide. That means every tanker passing through must travel within the territorial waters of either Iran or Oman. There is no alternate sea route.
Roughly 20 million barrels of oil flow through the strait each day. That’s equivalent to just under Americans’ daily usage and accounts for about one-fifth of global supply. Around 20 percent of the world’s liquefied natural gas also moves through Hormuz. In 2025 alone, the energy trade passing through the corridor was valued at roughly $600 billion annually, with nearly 3,000 ships transiting each month.
In short: if Hormuz is disrupted, the global energy market feels it almost immediately – and so do American consumers.
Why the UN Is Involved
The crisis isn’t just about naval deployments or military threats. It’s also about international law, specifically the UN Convention on the Law of the Sea (UNCLOS).
Adopted in 1982 after nearly a decade of negotiations, UNCLOS sets the ground rules for how countries use the world’s oceans. It defines territorial seas – extending 12 nautical miles from a country’s coastline – creates exclusive economic zones and establishes the legal framework for navigation through international waterways.
That last piece matters enormously when it comes to maritime chokepoints. There are roughly 110 straits worldwide, including some of the busiest shipping corridors on the planet: the Strait of Malacca in Southeast Asia, the Bab el-Mandeb linking the Red Sea to the Gulf of Aden and the Taiwan Strait. History shows how sensitive these passages can be. The closure of the Strait of Tiran by Egypt in 1967, for instance, helped trigger the Six-Day War.
The Strait of Hormuz is one of the most critical of them all. Because the channel lies within the territorial waters of Iran and Oman, UNCLOS created a special legal regime for straits like it known as “transit passage.”
Under this rule, ships have the right to move continuously and quickly through straits used for international navigation, even when those waters technically fall within a country’s territorial sea. The treaty is explicit on the point. Article 44 states that countries bordering such straits “shall not hamper transit passage,” and the right cannot be suspended.
In other words, the legal architecture of the oceans assumes that these corridors must remain open.
The politics, however, are more complicated. Oman has ratified UNCLOS. Iran signed the treaty but never ratified it. The United States hasn’t ratified it either, though Washington treats most of its navigational provisions as binding customary international law and regularly enforces them through Freedom of Navigation operations.
Despite those differences, the core principle – that major international straits must remain open – has broad global acceptance. In fact, it’s an especially consequential achievement of the post-World War II legal order: a UN-negotiated framework designed to ensure that the world’s maritime highways remain open for commerce and transit.
“States bordering straits shall not hamper transit passage and shall give appropriate publicity to any danger to navigation or overflight within or over the strait of which they have knowledge. There shall be no suspension of transit passage.”
UNCLOS, Article 44
Can Iran Legally Close the Strait?
Which brings us back to the $600-billion question: can Iran legally close the strait to retaliate against adversaries?
No.
Even before UNCLOS existed, the 1958 Geneva Convention on the Territorial Sea – which Iran did ratify – recognized that straits used for international navigation could not be arbitrarily closed. Under that earlier system, foreign ships enjoyed what is known as “non-suspendable innocent passage.”
UNCLOS later strengthened those protections through the transit passage regime.
The bottom line is straightforward: under either legal framework, a blanket closure of the Strait of Hormuz to international shipping would be extraordinarily difficult to justify under international law.
That said, coastal states do retain certain rights. They can regulate navigation for safety and may act against vessels engaged in hostile activities. But those powers are limited to specific conduct during transit – they do not extend to broader geopolitical disputes or retaliation for military strikes.
(Further, if Iran were to obstruct passage by military means, it would raise serious legal concerns under the UN Charter, which prohibits the unlawful use of force.)
How Do You Close a Body of Water?
All of this raises an obvious question: how does a country actually close a waterway?
Unlike a canal, it goes without saying that the open ocean can’t simply be shut. In practice, closing a strait means making passage so dangerous or economically risky that commercial shipping stops moving through.
There are several ways to achieve that.
Mines. One of the most effective methods is seeding shipping lanes with underwater mines. Submarines or fast-attack boats can deploy them quietly, turning major trade routes into a high-stakes gamble.
Missiles and drones. Coastal missile batteries or drone attacks can threaten passing vessels. Even occasional strikes can rattle the shipping industry. You don’t have to hit every ship – only enough to demonstrate the threat is real.
Harassment and seizures. Another tactic is harassment by swarms of small fast boats that board, detain or seize tankers. Iran used similar tactics during the Tanker War of the 1980s, and incidents have resurfaced periodically in recent years.
Insurance upheaval. The most powerful lever may not involve weapons at all. If insurers determine a waterway has become too dangerous, they may refuse to cover ships traveling through it. Without insurance, vessels cannot secure financing, cargo or crews. At that point, the waterway may not be physically blocked, but traffic collapses anyway.
In other words, straits like Hormuz are rarely actually closed, but rather economically closed, when risk, markets and fear accomplish what navies might otherwise attempt.
What Can the Global Community Do?
The UN doesn’t have a standing navy capable of reopening a blocked strait. What it does provide and which the U.S. played a central role in building, is a legal and diplomatic framework designed to keep maritime crises from spiraling into global economic shocks.
Through the Security Council, governments can convene emergency sessions, clarify legal obligations and in extraordinary circumstances, call for collective action. Meanwhile, UNCLOS establishes widely recognized rules for navigation that help stabilize expectations during moments of tension, reassuring markets and limiting the ripple effects of geopolitical crises.
For Washington, that matters.
Because when strategic chokepoints are threatened, clear legal rules and established diplomatic forums help contain risk and provide a foundation for global stability. And when the waters get especially rough, they provide a place to steady the ship.