Why Iran insists on controlling the Strait of Hormuz
Under a memorandum of understanding (MoU) between the United States and Iran, Washington agreed to lift its naval blockade of Iranian ports, issue a sanctions waiver for Iranian crude oil and petrochemical exports, and begin releasing a portion of Iran's frozen overseas funds.
The concessions were intended to secure unimpeded navigation through the Strait of Hormuz, passage through which had been disrupted amid the wider confrontation between the two countries.
Iran has continued to assert practical control over movement through its half of the strait, anchoring this position in a long-standing territorial sea claim over the waterway.
The sanctions waiver was subsequently revoked after renewed attacks on shipping in the strait were attributed to Iran, exposing the fragility of the arrangement.
UNCLOS Transit Passage Regime for International Straits
The United Nations Convention on the Law of the Sea (UNCLOS), 1982, governs navigation through straits used for international shipping. Articles 37 and 38 grant all ships and aircraft the right of "transit passage" — continuous, expeditious movement through a strait connecting one part of the high seas/EEZ to another — and Article 44 explicitly bars littoral states from suspending this right, distinguishing it from the more restrictive "innocent passage" regime applicable to ordinary territorial seas.
Key Details
- UNCLOS opened for signature in 1982; India ratified it in 1995
- Transit passage (Art. 38) is broader than innocent passage — it also covers overflight and submerged transit, and littoral states may regulate but not suspend it
- Littoral states retain limited regulatory powers over navigational safety, pollution control, and customs, but not suspension of passage (Art. 44)
- The Strait of Hormuz is the paradigmatic example of a strait to which the transit passage regime applies, connecting the Persian Gulf to the Gulf of Oman and the Arabian Sea
Iran's assertion of control conflicts with the transit passage principle that non-suspension is guaranteed under UNCLOS, which is why most maritime states, including the US, treat any Iranian blockade as a violation of customary international law even where UNCLOS is not directly binding on Iran.
Iran's Non-Ratification of UNCLOS and Its Alternative Legal Basis
Iran signed UNCLOS in 1982 but has never ratified it, so it is not bound by the convention's transit passage rules. Instead, Iran bases its claims on pre-UNCLOS instruments — principally the 1958 Geneva Convention on the Territorial Sea and Contiguous Zone, and the International Court of Justice's 1949 Corfu Channel case, which recognised a right of "innocent passage" (a narrower right than transit passage) through straits used for international navigation.
Key Details
- In 1959, Iran extended its territorial sea to 12 nautical miles along the strait and declared it would recognise only "innocent passage," not the broader transit passage regime
- The 1958 Territorial Seas Convention that Iran relies on itself states that innocent passage cannot be suspended through straits used for international navigation, creating an internal contradiction in Iran's position
- The US has also not ratified UNCLOS but, like most states, accepts transit passage as customary international law
The MoU's promise to reopen the strait runs up against Iran's decades-old legal position that it may restrict passage through its territorial waters — a doctrinal gap that keeps the strait's status contested even after diplomatic concessions.
Strategic Geography — The Strait of Hormuz as a Global Chokepoint
The Strait of Hormuz separates Iran from Oman's Musandam exclave and connects the Persian Gulf to the Gulf of Oman. It is the world's most important oil transit chokepoint, funnelling crude and refined product exports from Saudi Arabia, Iraq, UAE, Kuwait, and Qatar, alongside Iran's own exports.
Key Details
- Narrowest point is about 29 nautical miles (roughly 54 km) wide, with two 2-nautical-mile-wide shipping lanes (inbound and outbound) separated by a buffer zone
- Around a third of global seaborne crude oil trade transits the strait, alongside significant LNG and refined-product flows
- Littoral states are Iran (north) and Oman (south, via the Musandam Peninsula)
- Comparable global chokepoints tested by UPSC include the Strait of Malacca (India-China-ASEAN trade) and Bab-el-Mandeb (Red Sea-Gulf of Aden)
Iran's geographic position astride the narrowest, most heavily trafficked segment of the strait gives it outsized leverage over global energy flows, which is the strategic logic behind its insistence on retaining a say over passage despite the MoU's terms.
- Strait of Hormuz narrowest width: approximately 29 nautical miles (54 km); shipping lanes are 2 nautical miles wide each way
- Roughly one-third of global seaborne crude oil trade transits the strait
- Iran extended its territorial sea to 12 nautical miles in 1959, restricting recognised passage to "innocent passage" only
- UNCLOS Articles 37, 38, and 44 establish and protect the transit passage regime; India ratified UNCLOS in 1995
- India now sources approximately 70% of its crude oil imports from outside the Strait of Hormuz, per the Ministry of Petroleum and Natural Gas, though LPG imports remain heavily dependent on the route