Iran and the United States have made bold statements about the Strait of Hormuz. Iran says it has the right to police it, demanding fees from transiting ships to pay for reconstruction from an illegal war. The U.S. says it has a right to blockade it, cutting off Iran from lucrative sea lanes in its own waters.
But what does international law say? And what might this all mean for the shipping lanes crucial to global commerce going forward?
Experts debate some of the details. But most agree Iran is overstepping its rights in one way or another, and that the conclusion reached by the U.S. and Iran will be of enormous consequence. If anyone is allowed to make the Strait of Hormuz a tollbooth, decades of carefully crafted international law will be shredded, nudging the maritime world back toward the days of mercurial sultans and Barbary pirates.
Why We Wrote This
In the Strait of Hormuz, Washington and Tehran are testing the boundaries of international laws that have managed the seas remarkably well, protecting freedom of navigation and facilitating a global economy. This war could roll back the clock on maritime norms – or strengthen them.
Which international rules apply?
The law that usually holds sway in maritime disputes is the United Nations Convention on the Law of the Sea, or UNCLOS, ratified by 171 nations, including Oman, which claims parts of the strait as its territorial waters.
Under UNCLOS, the Strait of Hormuz is an international strait, meaning it can’t be closed for any reason. So long as a ship doesn’t dally in an international strait, it has an “absolutely unsuspendable right of passage,” says Marc Weller, director of the Global Governance and Security Center at Chatham House, a London-based think tank.
One issue here is that neither the U.S. nor Iran has officially ratified UNCLOS. In this case, legal rights are generally determined by what is called customary international law, a set of near-universal expectations based on countries’ policies and practices.
When it comes to maritime trade routes, customary law gives nations slightly more leeway in their own territorial waters. Yet even customary law recognizes the right of innocent passage. That means ships can move through another nation’s waters so long as they do so expeditiously and do not threaten or take advantage of the host nation.
Who is in violation and how?
Some experts say elements of UNCLOS have effectively become customary law, and, as a result, the Strait of Hormuz is an international strait with right of passage, regardless of whether Iran ratified the treaty. Iran rejects that argument.
“They never officially recognized the Strait of Hormuz as an international strait and therefore they exercised the option of hampering shipping traffic any time they wanted,” says Farzin Nadimi, a senior fellow at the Washington Institute for Near East Policy.
Yet the Islamic Republic has never done anything remotely on this scale. And even if Iran is not bound by UNCLOS, the right of passage in customary law is clear.
Under innocent passage, “one would expect any such measures [by Iran] to be directed only at U.S. or Israeli vessels, rather than all ships,” says María García Casas, a professor of public international law at the Autonomous University of Madrid, in an email interview.
There is another wrinkle. In war, the laws of naval warfare apply to combatants. For neutral states, that shouldn’t make much difference. Ships flagged to neutral countries should be able to proceed unimpeded.
However, U.S. President Donald Trump initially said all traffic through the area would be blocked. Military officials later said the blockade applied only to Iran-linked vessels. A BBC attempt to verify the impact of the American blockade by analyzing ship tracking data was inconclusive.
The laws of naval warfare would also complicate a proposal for the U.S. to escort tankers through the strait. “Any merchant vessel traveling in a convoy under the protection of a belligerent warship is subject to attack,” says Natalie Klein, a legal expert at the University of New South Wales in Sydney, in an email.
What does the war mean for shipping in the future?
Here, most experts agree that the stakes are extremely high. Until the Iran war, the international law governing the seas “was going so fine that no one thought about it,” says Mark Nevitt, a retired U.S. Navy commander, now a professor at Emory Law School in Atlanta.
The war could blow a hole through those laws.
“If we had an outcome where the U.S. negotiates a deal that somehow accepts Iranian and Omani control over the strait, that would … challenge the universal agreement that all straits are open to all ships of all nations, under all circumstances. And that would be very dangerous,” says Mr. Weller of Chatham House.
To find similar examples, historians need to go back centuries. A Financial Times report examining the practice of taxing international waterways points to the fee Denmark exacted on vessels passing between the North Sea and Baltic Sea, starting in the 15th century. Not much later, the Portuguese Empire took control of Hormuz Island to control and profit from trade in the Indian Ocean.
Famously, America’s first wars as an independent nation in the early 19th century were against Barbary pirates who demanded a fee to leave ships in the Mediterranean unharmed.
Professor Klein hopes the resolution of this war will strengthen international law. “To collect tolls would be entirely contrary to navigational rights that have been enjoyed for decades through international straits,” she says. “If anything, the conflict has highlighted how important navigational rights are for all states and why those rights need to be protected.”
