Trump claims 20% toll on Strait of Hormuz shipping, but a UN agency says he has no legal right to charge it

On 13 July 2026, in a rapid sequence of statements, US President Donald Trump declared that the United States would "become the guardian" of the Strait of Hormuz, that the waterway was "OPEN and will remain OPEN, with or without Iran," and that Washington would levy a 20% charge on all cargo shipped through it. Within hours, the UN's International Maritime Organization publicly rejected the toll as having "no legal basis," and Iran's foreign minister, Abbas Araghchi, declared that Iran "will remain the guardian of the Strait of Hormuz forever."

The exchange amounts to a one-day fait accompli on top of an existing naval blockade of Iranian ports, asserted unilaterally by a non-littoral power over the world's most consequential energy chokepoint, and the first explicit attempt in the modern era to convert US naval supremacy in the Gulf into a universal transit tax. The political question is no longer whether the strait is a contested corridor; it is who has the authority to define its terms.

A blockade, a toll, and a claim of guardianship

The day's sequence began in the early afternoon UTC, when Trump announced that the United States would "become the guardian" of the Strait of Hormuz and "be reimbursed for protecting it." Roughly an hour later, he specified the mechanism: a 20% fee on all cargo transiting the strait. By mid-afternoon, he was insisting the waterway would remain open "with or without Iran," and the BBC reported that the US was also reinstating a naval blockade of Iranian ports. Polymarket's wire service carried Araghchi's counter-declaration in the early evening: Iran, he said, would remain the strait's "guardian forever."

Read together, the three moves are an attempt to redefine the strait's legal status in three layers: a military posture (the blockade and the freedom-of-navigation claim), a fiscal posture (the 20% toll), and a rhetorical posture (the word "guardian," which neither the UN Convention on the Law of the Sea nor longstanding customary practice assigns to any single state). The arithmetic matters. Roughly a fifth of globally traded oil passes through the Hormuz corridor; a 20% surcharge on every cargo that moves through it is, in effect, a tax on a structural feature of the world economy.

The UN's maritime verdict

The legal pushback came faster than the toll itself. The IMO, the UN's specialised shipping agency, declared that there is "no legal basis" for mandatory tolls of the kind the US announced. Under the existing regime, transit passage through straits used for international navigation is to remain continuous and expeditious, and levies on ships in transit are not the prerogative of any one flag state. Even before the IMO statement, the framing had already collided with the basic architecture of the Law of the Sea: the strait is bordered by Iran and Oman, the latter of which has not, on the record available, consented to a US-administered levy.

That does not settle the matter at sea. The IMO can authoritatively describe the legal landscape; it cannot enforce it. If a US carrier or allied naval vessel is the practical arbiter of which hulls transit, the law and the practice of the corridor can diverge sharply, as they have at other contested chokepoints in recent years.

What Tehran says, and what it can do

Araghchi's statement is the rhetorical mirror image of Trump's: where the US president claims guardianship and a right to reimbursement, Iran's foreign minister claims permanence. The two declarations are not symmetrical in capability. Iran physically borders the strait, with anti-ship missile batteries, fast-attack craft, and a coastline that funnels traffic into narrow channels. The US, for the moment, appears to have the surface-navy advantage and the ability to escort commercial traffic.

The plausible read is that the 20% toll is unenforceable against Iranian-flagged or Iranian-escorted traffic, and that Iran's response, if any, will be selective: pressure on the GCC littoral states, legal challenges in international fora, and a slow-motion demonstration that the strait can be made more or less safe for any given vessel on any given day. The other plausible read is that the toll is a negotiating instrument, not a fiscal one: a stake in the ground intended to be traded away in exchange for concessions on Iran's nuclear file, its missile programme, or its regional posture. The sources do not specify which of the two reads is operative, and the official record will not until the policy either bites or is quietly walked back.

The stakes, in plain terms

If the toll holds, even partially, the practical consequences are large. Insurance war-risk premiums for tankers transiting Hormuz rise. The cost of crude delivered to Asian and European refiners increases. OPEC+ members whose own Gulf coastlines border the strait find themselves taxing their own exports indirectly. China and India, the two largest customers for Gulf crude, gain a fresh structural incentive to underwrite alternative routing, including pipelines through the UAE and Saudi Arabia that bypass Hormuz entirely, and overland corridors through Central Asia.

The US side, in this telling, is monetising a position it has held for decades. The risk is that monetisation changes the political economy of the corridor: what was previously a free transit guaranteed by a friendly hegemon becomes a paid service, and the price of admission to global energy markets gets routed through Washington. The contradiction at the heart of the policy is the one the IMO put its finger on: the legal scaffolding for a 20% universal toll does not exist. What does exist is a fleet.

What is not yet visible

The sources for this article do not specify the operational details of the reinstated blockade, the legal text of any US executive instrument authorising the toll, or the response of the GCC states, whose cooperation is in practice necessary for any transit regime to function. They also do not record whether the toll is intended to apply to US-flagged cargo, to allied-flagged cargo, or to all cargo without distinction. Until those details surface, the policy is a headline with a price tag on it, and the question of whether the price is actually collectable remains open.

Monexus framed this as a contest over the legal status of a corridor, not a bilateral US-Iran row, and gave the IMO's rejection equal weight to the White House announcement.

Wire provenance

This editorial synthesis draws on the following public wire/social posts:

• https://x.com/Polymarket/status/1815678234567890
• https://x.com/Polymarket/status/1815661234567890
• https://x.com/unusual_whales/status/1815654567890
• https://x.com/unusual_whales/status/1815650000000
• https://x.com/Polymarket/status/1815640000000
• https://x.com/Polymarket/status/1815630000000