Qeshm Island, the largest in Iran, is located in the Strait of Hormuz
Iran closed the Strait of Hormuz at the end of Monday and threatened to set fire to ships that try to cross it. How does this affect us?
O Strait of Hormuz it is a choke point at the entrance to the Persian Gulf. It is used to transport around 20% of global daily oil consumption.
Iran effectively controls this crucial sea route because it is a coastal state bordering this stretch of water. The place is, as the name suggests, too narrow to avoid sailing in waters claimed by Iran.
This raises complex legal questions about whether it is actually possible for Iran to block the strait and what recourse other states have if it does so, as is happening now, on the sidelines of the .
Citing Iranian media, it said that the commander of Iran’s Revolutionary Guard ordered to close the Strait of Hormuz and will set fire to any ship that tries to pass. This measure comes after the assassination of the Iranian Supreme Leader, the Ayatollah Ali Khameneiin an Israeli attack.
Laws, agreements and contracts…
Returning to the Strait and geopolitics: this reality is far from new, and the legal frameworks that govern international maritime activity have developed over centuries. At its core is the lex mercatoria — the “law of merchants” — a body of transnational commercial law that emerged organically from the practices of merchants operating across borders.
Within this broader framework lies the lex maritimaor customary maritime law, which has long adapted to the dangers of sailing across vast oceans.
A lex maritima it originated from the shared practices of sailors and merchants. Your purpose? Managing the unpredictable nature of maritime trade requires coherent and stable rules.
Another concept that is mandatory to mention is that of free seaor “the free sea”, exposed by the jurist Hugo Grotius in 1609. It is one of the most enduring principles of this legal tradition. The Dutch argued that the high seas should remain atopen to all for peaceful navigation and commerce.
This conveniently legitimized the ambitions of European colonial powers (such as Portugal) by granting them unrestricted access to global shipping lanes at a time when control of maritime trade promised immense economic and strategic advantage.
The Changing Frontiers of Maritime Law
One of the most fundamental questions in maritime law is: after all, Where do a nation’s territorial waters end and the high seas begin?
After World War II, a series of conferences culminated in the United Nations Convention on the Law of the Sea (UNCLOS)where the usual 3 nautical miles (5.56 km) of territorial waters that States could claim as their own were expanded.
This narrow limit was more rooted in historical naval reach—the so-called “cannon shot rule” — than in modern geopolitical or environmental realities.
In 1959, Iran took the unusual step of unilaterally extending its territorial sea to 12 nautical miles despite not being a party to UNCLOS.. Two decades later, following the 1979 Iranian Revolution and the U.S. Embassy hostage crisis, Washington became increasingly nervous about the security of oil flows from the Persian Gulf.
Such concerns intensified during the Iran-Iraq War, especially when Iran began using small islands in the Strait of Hormuz to deploy military forces and threaten commercial shipping.
UNCLOS and the new rules of the sea
One of the main commitments of UNCLOS was the expansion of territorial waters for States that ratified the treaty.
In return, UNCLOS replaced the older concept of “innocent passage” — which allowed only surface navigation through territorial seas — by the broader notion of “passage in transit”.
Under this regime, vessels and aircraft from other States are given the right to travel not only on the surface, but also under the sea and through the airspace above straits used for international navigation.
As an article in , although 169 States have ratified UNCLOS, Both Iran and the US remain notable absences.
This means that, on the one hand, the Iran does not benefit from the broader 12 nautical mile limit recognized by UNCLOS, and the US cannot claim the agreement’s protections for transit passage through strategic chokepoints. A mess.
And now?
Without significant political change in Tehran, it is unlikely that both Iran and the US will alter their position on the adoption of UNCLOS.
After repeated threats from Iran to close the strait, triggering a new conflict, it finally materialized — even with the US Navy maintaining a constant presence in the region. While, before, a fragile but persistent balance, now, not even that was maintained.
The consequences? You’ll probably feel them at the gas pumpin the coming weeks. And we already know… when fuel prices risethe prices of most .
