Iran Escalates Territorial Claims Over Strait of Hormuz

On May 20, 2026, the Islamic Revolutionary Guard Corps Navy announced that it had "coordinated" the transit of 26 vessels through the Strait of Hormuz in the preceding 24 hours — language that framed passage through the world's most critical oil chokepoint not as a right under international law, but as a privilege granted by Tehran [1]. The statement capped a three-month escalation in which Iran has moved from rhetorical claims of sovereignty to operational enforcement, boarding merchant ships, laying sea mines, and publishing new maps that designate the strait as a "controlled maritime zone" [1].

The result is the largest disruption to global energy supply since the petroleum age began. Where the 1973 Arab oil embargo removed roughly 6% of world supply, the effective closure of Hormuz has taken approximately 20% offline — more than three times the magnitude [2]. Brent crude surged past $120 per barrel in March and WTI has traded above $112 as of mid-May, up 75% year-over-year [3][4].

The Legal Argument Iran Is Making — and the Ambiguity It Exploits

Iran's territorial claim rests on a deliberate rejection of the legal framework most of the world considers settled. Under the 1982 UN Convention on the Law of the Sea (UNCLOS), the Strait of Hormuz qualifies as an "international strait" subject to a "transit passage" regime — meaning coastal states cannot suspend or impede the continuous and expeditious movement of ships and aircraft [5]. Transit passage is broader than "innocent passage," the older standard that gives coastal states more discretion to regulate or deny passage they deem harmful to their security [6].

Iran signed UNCLOS in 1982 but never ratified it. Neither did the United States. This creates what Elizabeth Mendenhall, an associate professor of marine affairs at the University of Rhode Island, has described as a situation where "the U.S. and Iran are living in two different worlds when it comes to the international laws governing the strait" [7]. With 171 countries having ratified UNCLOS, neither superpower is formally bound by its compromise provisions.

Tehran's legal strategy has three prongs. First, Iran invokes the 1949 Corfu Channel case and the 1958 Territorial Seas Convention — pre-UNCLOS instruments that recognize only innocent passage through territorial straits [6][7]. Second, Iran argues that it is a "persistent objector" to transit passage, a doctrine under customary international law that exempts states from emerging legal norms they have consistently opposed. Iran and Oman both argued against transit passage during the UNCLOS negotiations [7]. Third, the IRGC's Persian Gulf Strait Authority has published new maps asserting a "controlled maritime zone" over the strait, effectively claiming operational jurisdiction beyond what even innocent passage would permit [1].

The persistent objector argument is the most legally provocative. Legal scholars remain split on whether transit passage has hardened into customary international law binding on all states, including non-ratifiers [6][7]. If it has not — and some law of the sea specialists argue it has not — then Iran's claim, while rejected by Western governments, sits in a zone of genuine legal ambiguity rather than clear-cut illegality.

There is, however, an internal contradiction in Iran's position. The 1958 Territorial Seas Convention that Tehran cites as authority explicitly prohibits suspending innocent passage through territorial straits [7]. Iran claims the right to do precisely that.

The Economic Shock: Twenty Percent of Global Supply, Gone

Before the crisis, the Strait of Hormuz carried approximately 20.9 million barrels per day of crude oil and petroleum products in the first half of 2025, accounting for roughly 20% of total world petroleum liquids consumption and 34% of all seaborne crude trade [8][9]. About 20% of global LNG trade also transited the strait, with 83% of those cargoes bound for Asian markets [8].

Source: EIA / IEA

Data as of Mar 1, 2026CSV

By March 2026, flows had collapsed to approximately 2.1 million barrels per day — a 90% reduction [8]. The economic impact has been immediate and severe.

The Dallas Federal Reserve estimated that the closure lowered global real GDP growth by an annualized 2.9 percentage points in the second quarter of 2026, with WTI averaging $98 per barrel under a one-quarter closure scenario [2]. A two-quarter closure pushes prices to $115; a three-quarter closure to $132 [2]. The World Bank's April 2026 Commodity Markets Outlook called it the "largest oil market shock in history" [3].

Source: Dallas Fed / EIA

Data as of May 1, 2026CSV

The comparison to prior disruptions is stark. The 1973 Arab oil embargo removed 4.5 million barrels per day — about 6% of global supply. The 1979 Iranian Revolution took 4% offline. The 2019 Abqaiq-Khurais drone attack on Saudi Arabia briefly knocked out 5.7 million barrels per day but was repaired within weeks [2][10]. The current crisis has removed roughly 18–19 million barrels per day with no clear end in sight.

Source: FRED / EIA

Data as of May 18, 2026CSV

UNCTAD has warned that the disruption reaches far beyond petroleum, affecting nine major commodity categories including petrochemicals, fertilizers, and aluminum — supply chains concentrated in the Gulf region [11]. The World Economic Forum noted that 30% of global desalinated water production depends on Gulf-based energy inputs now constrained by the crisis [11].

Who Stands to Lose: Asia's Exposure

The countries most dependent on Hormuz-transited energy are not in the West. China accounts for 37.7% of total strait flows, India for 14.7% [12]. Japan, South Korea, and Southeast Asian economies import between 60% and 80% of their crude through the waterway [12].

Chinese imports through the strait fell from 4.45 million barrels per day before the war to approximately 222,000 barrels per day in April 2026 [13]. India's supplies dropped from 2.8 million barrels per day in February to 247,000 in March, with India assessed as having only a 30-day buffer against prolonged disruption [12][13].

These dependencies have produced a diplomatic dynamic sharply at odds with Western expectations. China and Russia vetoed a UN Security Council draft resolution on April 7 that would have demanded freedom of navigation in the strait, even as Beijing publicly called for "all parties" to ensure "stable and unimpeded energy supply" [14]. India resumed purchases of Iranian oil and gas after a seven-year hiatus, securing safe passage for its vessels from Tehran under a temporary U.S. exemption [14]. The Indian Navy deployed warships near the Persian Gulf on standby for merchant vessel escort [14].

The divergence between public statements and actual behavior is significant. Beijing's rhetoric demands de-escalation and free navigation; its veto protected Iran's leverage. India's petroleum ministry has emphasized that 70% of crude imports now come from outside Hormuz-dependent routes [12], yet New Delhi simultaneously cut direct deals with Tehran — a pragmatic hedge that undercuts the U.S.-led isolation strategy.

Gulf states, theoretically among Iran's most immediate targets, have pursued their own track. A coalition of 22 countries including the UAE, Bahrain, the UK, France, Germany, and Japan signed a statement declaring willingness to "contribute to appropriate efforts to ensure safe passage" [14]. Saudi Arabia's East-West pipeline can redirect approximately 4 million barrels per day to Red Sea ports — one-fifth of the shortfall — though regional security concerns limit its effectiveness [2].

Iran's Military Capability: From the Tanker War to Now

Iran's ability to enforce its claims is qualitatively different from what it possessed during the 1984–1988 Tanker War, the last major confrontation over strait traffic. During that conflict, Iran lacked effective anti-ship cruise missiles, resorting to repurposed air-to-ground Mavericks and French-made AS-12s designed for armored vehicles [15]. Western arms embargoes degraded the readiness of its U.S.-supplied naval equipment throughout the Iran-Iraq War [15].

The IRGC Navy has since invested heavily in asymmetric capabilities. Its "mosquito fleet" comprises an estimated 500 to over 1,000 fast attack craft, many armed with C-802 anti-ship cruise missiles with a 120-kilometer range [16][17]. In February 2025, the IRGC unveiled the Heydar-110, a carbon-fiber catamaran capable of 110 knots — reportedly the fastest operational military combat boat in the world [16]. The force has also deployed unmanned surface vessels, including the Ya Mahdi high-speed drone boat equipped with three rocket launchers and capable of shore-guided remote operation [16].

Beyond fast boats, Iran has layered defenses including coastal anti-ship missile batteries, small submarines, and — critically — sea mines. The IRGC began laying mines in the strait in late February 2026, a tactic that proved highly effective in the Tanker War, when a single mine struck the USS Samuel B. Roberts in 1988 [16][17].

On the U.S. side, the military buildup preceding the February 2026 strikes was the largest American deployment to the Middle East since the 2003 invasion of Iraq [18]. The USS Abraham Lincoln carrier strike group arrived in late January with guided-missile destroyers, cruisers, and embarked aircraft [18]. But the strike on Naval Support Activity Bahrain on February 28 — headquarters of the U.S. Fifth Fleet — damaged communications infrastructure and demonstrated Iran's ability to directly target the command-and-control backbone of American naval operations in the Gulf [18].

In May 2026, the U.S. launched "Project Freedom," an operation to break Iran's hold on the strait using warship escorts for commercial convoys [19]. The operation echoed the 1987–1988 "Earnest Will" tanker reflagging and escort operation, but against a far more capable adversary.

The Domestic Political Engine

The Strait of Hormuz claim did not emerge from a unified Iranian government. The February 2026 U.S.-Israeli strikes killed Supreme Leader Ali Khamenei, producing a leadership succession crisis that has intensified factional competition [20]. Khamenei's son was appointed successor, but the transition has exposed open divisions within the clerical establishment between hardliners demanding further escalation and pragmatists warning about the cost of continued conflict [20].

The IRGC has emerged as the dominant institutional actor. The Revolutionary Guard controls the "mosquito fleet," the mine-laying operations, and the Persian Gulf Strait Authority that published the new maritime jurisdiction maps [1][16]. Iran's president and parliament speaker have sought the removal of Foreign Minister Abbas Araghchi, accusing him of following IRGC Commander-in-Chief instructions in nuclear negotiations without informing the elected government [20].

This factional dynamic shapes the toll proposal. In late April, Iran presented a 10-point peace plan to the United States that included reopening the strait in exchange for toll-collection rights and postponement of nuclear negotiations [21]. The proposal treats the strait as a bargaining chip — leverage to be exchanged for sanctions relief and reconstruction funding, rather than a permanent assertion of operational control.

President Trump called the toll concept "a beautiful thing" [22], a statement that alarmed maritime law experts and U.S. allies who saw it as implicitly legitimizing Iran's sovereignty claim. Subsequent U.S.-China alignment on opposing tolls and militarization of the strait [23] suggested the comment may have been a negotiating gambit rather than a policy position.

The Toll Precedent and Global Chokepoints

No coastal state has imposed mandatory tolls on a natural international strait in the post-1945 era [22][24]. The historical precedents Iran's proposal evokes are not encouraging. Denmark collected "sound dues" at Kronborg Castle from 1429 until a coalition of trading powers, including the United States, forced their abolition through the 1857 Copenhagen Convention [22]. Ottoman authorities charged passage fees through the Dardanelles until the practice was abolished.

Turkey collects limited administrative fees in the Bosphorus and Dardanelles under the 1936 Montreux Convention, but these are not considered full transit tolls and are governed by a multilateral treaty [22]. The Suez and Panama Canals charge fees, but both are artificial waterways — constructed infrastructure, not natural straits subject to freedom-of-navigation principles [24].

Donald Rothwell, a professor of international law at the Australian National University, has noted that UNCLOS Article 44 states that coastal states "shall not hamper transit passage" — and "that word has been universally understood as prohibiting toll imposition" [24].

The International Maritime Organization stated that Iran's proposal would "set a dangerous precedent" [24]. Defence analyst Jennifer Parker warned: "Should you start to see a trend that reduces freedom of navigation, it would fundamentally change maritime trade" [24].

The concern extends well beyond Hormuz. If Iran's toll claim were accepted or left unchallenged in practice, it would offer a template for other contested chokepoints. China's claims in the South China Sea, Indonesia's assertions around the Strait of Malacca, and renewed scrutiny of the Turkish Straits all loom as potential flashpoints where coastal states might assert similar authority [22][24]. Some international law scholars have argued that a negotiated joint-monitoring regime — perhaps involving Oman, which shares the strait — might produce more stability than the current legal vacuum in which two non-ratifiers of UNCLOS contest the fundamental rules [7]. But any such arrangement would need to avoid legitimizing unilateral toll extraction, a line that most maritime states consider non-negotiable.

What Comes Next

As of late May 2026, the crisis remains unresolved. Iran's 10-point proposal is on the table but has not been accepted [21]. The IRGC continues to claim coordinating authority over strait traffic [1]. WTI crude trades above $112 [4]. The U.S. Navy is conducting convoy escort operations under fire [19]. And the legal question at the center of the dispute — whether transit passage through the Strait of Hormuz is a binding rule of customary international law or a contested norm that Iran has successfully evaded — remains unanswered by any authoritative tribunal.

The stakes extend far beyond the price of oil. The post-1945 maritime order is built on the principle that natural straits connecting international waters remain open to all. If that principle can be suspended by a sufficiently motivated state with enough fast boats and sea mines, the implications reach every chokepoint on the map.