LONDON, July 12 — The legal architecture governing the Strait of Hormuz is facing its most serious test in decades, and the shift is unmistakable. What was once a settled regime of international navigation is now a flashpoint where maritime law, national security, and regional power politics collide. The United Nations Convention on the Law of the Sea, which came into force in 1994, provides the framework.
Under Article 37, straits used for international navigation—and the Strait of Hormuz is the critical example—are subject to what the convention calls “transit passage.” This allows ships and aircraft to pass freely and without hindrance. It is not a privilege granted by coastal states; it is a right under international law.
But the convention’s application here is complicated. Iran has signed UNCLOS but never ratified it. Tehran generally respects the transit passage regime in practice, but it also claims the right to regulate passage for environmental or security reasons, citing Article 233.
The United States and most other nations reject any unilateral closure of the strait outright. The U.S. itself is not a party to UNCLOS, though it recognizes the convention’s provisions as customary international law.
The older 1958 Geneva Convention on the Territorial Sea also applies to the strait. That dual legal foundation matters: a unilateral closure by Iran would violate international law and could trigger action by the United Nations Security Council.
The legal stakes
The International Maritime Organization, based in London, sets shipping safety standards. But the IMO has no enforcement mechanism in a crisis. That reality leaves the legal regime dependent on the willingness of states to uphold it.
The trend underneath is that Iran has increasingly tested the boundaries of what it can claim. Tehran argues that environmental protection or security concerns give it the authority to restrict passage.
The U.S. and its allies see this as a creeping expansion of coastal-state control over international waters. The U.S. has responded with Freedom of Navigation Operations—FONOPs—conducted in the strait to challenge what Washington considers excessive claims. These operations occurred in 2021 and 2023, and they send a clear signal: the United States will not accept a reinterpretation of the law of the sea that erodes transit passage.
What happens next
Watch this space. The legal arguments are not abstract. If Iran were to attempt a closure, the response would likely be immediate and multilateral.
The UN Security Council could act. The U.S. Navy, which patrols the region, would almost certainly resume or intensify FONOPs.
The Strait of Hormuz is a chokepoint for global energy supplies. A closure would not just be a legal violation—it would be an economic shock. But the legal framework, while contested, remains the primary tool for managing that risk.
The convention may be three decades old, but its relevance has never been sharper. What’s changing is the willingness of some states to push against its boundaries.
The question is whether the system holds.
