• Iran's Persian Gulf Strait Authority warns vessels against using "illegal routes" in the Strait of Hormuz, threatening financial losses and future passage restrictions.
  • The move follows a multinational demand for reopening the waterway and reports of tankers struck after alleged noncompliance.
  • Energy markets and shipping face heightened uncertainty as negotiations over transit arrangements continue.

Iran's Persian Gulf Strait Authority (PGSA) has issued a stark warning to vessels in the Strait of Hormuz, stating that using "illegal routes" will result in financial losses, loss of life, and restrictions on future passage. The warning, issued on September 27, signals an effort to tighten control over shipping through the critical chokepoint, though it does not announce a full closure of the strait. On October 2, the PGSA claimed that three Emirati tankers—Al Ruwais, Sinbad, and Mersin Prosperity—had been struck after being placed on a noncompliance list.

The development comes amid escalating tensions: on September 24, around 80 countries demanded the urgent reopening of Hormuz and condemned attacks affecting trade and energy security. Iran's route restrictions, attacks on shipping, and the U.S. blockade of Iranian ports are overlapping with negotiations over reopening the waterway. "Illegal" reflects Iran's characterization, not an established international legal finding.

Market and Operational Fallout

Hormuz carried approximately one-fifth of global oil and gas flows before the conflict, making restrictions consequential far beyond the region. However, traffic is impaired rather than uniformly stopped. Reuters (TRI) reported 33.7 million barrels of crude exported through the strait during the week starting September 20, as measured up to September 25. Energy markets face upward pressure on oil and gas prices, while shipowners, charterers, and cargo buyers confront increased operational uncertainty. The PGSA explicitly directed its warning at vessels, owners, masters, and crews.

Iran's economy is also a factor: Tehran seeks relief from the U.S. blockade of its ports, which Reuters describes as choking its economy. Control of Hormuz is both a military instrument and bargaining leverage. Meanwhile, alternative export routes are not uncomplicated—Houthi attacks on Saudi Aramco (2222.SR)'s East–West pipeline prompted the company to increase exports through Hormuz in September and October.

Traffic statistics need careful interpretation. Reuters' commodity-vessel counts and a U.S. official's claim of roughly 60 commercial vessels transiting on September 23 cover different categories and verification standards. Ships operating with transponders switched off can escape tracking counts, so these figures do not support a precise estimate of total throughput.

Diplomatic and Legal Dimensions

Iran is attempting to make passage conditional on its approval and preferred routes, while Washington is pressuring Tehran to stop interfering with shipping and maintaining a counterblockade of Iranian ports. Reuters reported discussions about a phased arrangement linking reopening Hormuz to lifting the U.S. blockade. The legal distinction matters: regulating navigation for genuine safety purposes is not the same as asserting an unrestricted right to deny passage. An American Society of International Law analysis explains that both relevant passage frameworks—transit passage and non-suspendable innocent passage—prohibit unjustified blocking of vessels. Iran disputes aspects of the transit-passage regime, and wartime maritime law adds complexity.

Stakeholder effects include direct risks to seafarers, higher energy costs for consumers and businesses, complications for Gulf exporters, and a diplomatic standoff between Iran's asserted security interests and other states' demands for navigational freedom.

Background and Outlook

The crisis developed after U.S. and Israeli strikes on Iran beginning February 28, 2026. Iran subsequently heavily restricted Hormuz traffic; the United States later imposed a blockade targeting shipping to and from Iranian ports. Negotiations over transit arrangements predate this warning. On August 4, Reuters reported that Iran sought control over inbound shipping and oversight of outbound traffic under a temporary arrangement being discussed with Oman. The following day, the BBC reported Iran's statement that an agreement with Oman was in its final stages, with a proposed temporary route lasting two to four months.

Two connected developments are important: Red Sea insecurity, with Houthi attacks weakening alternative routes, and a partial LNG recovery—Reuters reporting cited by Iran International indicated 19 LNG cargoes transited Hormuz in September, the highest monthly number since the war began.

Looking ahead, short-term scenarios include more vessel interceptions or attacks if Iran enforces its preferred routes more aggressively, or a negotiated transit arrangement that could improve flows if paired with relief from the U.S. blockade. Longer-term, persistent disruption could strengthen pressure to diversify export routes, though alternatives remain vulnerable. An Iranian-controlled authorization system could become a continuing source of diplomatic and legal confrontation. The most useful near-term indicators are a published route map and enforcement deadline, independently confirmed maritime incidents, sustained oil and LNG throughput, and an implemented agreement linking passage to blockade relief.

A request for comment from the PGSA was not immediately returned.

Correction: An earlier version of this article misstated the date of the PGSA warning. It was issued on September 27, not September 26.