The Strait of Hormuz is a 167 km long and 33–39 km wide (at its narrowest point) international waterway, connecting the Persian Gulf and the Gulf of Oman. It is a most important maritime choke point that has grabbed international headlines after the Iran–Israel–US war. Before the war, sea commerce through the Strait of Hormuz constituted approximately 140 containers per day, which has now dwindled to 5–6 containers per day, a 95% reduction from pre-war levels. Around 3,000 shipping vessels are impacted due to the blockade, bottling up 450,000 TEU capacity since 28th February 2026.

The closure of Hormuz was a classic asymmetric warfare strategy employed by Iran to choke the flow of oil, pressurising the US Gulf allies as well as the USA into abandoning the attacks on its territory. Iran employed several tactics to block the strait, including the use of coast-based weapons such as missiles, drones, and fast attack speed boats equipped with torpedoes. Iranians also retain underground unmanned as well as manned weapon systems capable of launching attacks on naval vessels passing through the narrow (3 km) shipping lanes in Iranian as well as Omani territorial waters comprising the Strait.

This is the first time that the Iranians have resorted to full closure of the Strait of Hormuz, as in the past, selective blockade and interdiction tactics were employed in response to periodic threats. In the 1980s, during the Iran–Iraq war, the Iranians attacked Kuwaiti and Saudi shipping vessels in response to those countries’ perceived support for Iraq, but did not interfere with the sea traffic of neutral countries.

Iran and Iraq both attacked each other’s oil tankers during the eight-year war, but refrained from attacking the rest of the sea traffic. Between 2019 and 2024, some selective targeting was resorted to by Iran in response to international sanctions, for example, the seizure of Stena Impero in 2019 and MSC Aries in 2024, but generally, sea commerce continued unscathed.

The current sea commerce dependency matrix of the Strait of Hormuz includes 40% of crude oil needs of China, 30% of refined as well as crude jet fuel needs of the EU, 90% of crude oil needs of Japan, 80% of crude oil needs of South Korea, 45% of crude oil plus 50% of gas needs of India, 80% of crude oil needs of Pakistan, and 85% of crude oil needs of Vietnam.

While China can withstand the disruptions, albeit at a high cost, due to its piped oil supply lines from Russia and alternative sources such as Central Asia, Australia and Norway, other Asian nations such as Japan, South Korea, Vietnam, India and Pakistan are heavily impacted by the supply chain disruption of oil and gas from the Middle East.

The shipping lanes in the Strait of Hormuz are primarily within Omani territorial waters, and Iran alone does not exercise territorial rights over those waters

The shipping lanes in the Strait of Hormuz are primarily within Omani territorial waters, and Iran alone does not exercise territorial rights over those waters

The closure of an international strait brings back memories of naval blockades and quarantines in the past, such as the British naval blockade of German ports from naval choke points like the English Channel and the North Sea, leading to serious shortages of everyday commodities in Germany. In the Second World War, the US Air Force and Navy interdicted sea lanes, targeting Japanese merchant ships while abandoning rules to search and secure the targeted ships’ crew before attacks; acts that would constitute illegality in the light of current international law.

In 1962, a naval blockade called a “Naval Quarantine” was employed by the USA to prevent the supply of offensive missile systems to Cuba. The term blockade was moderated to quarantine, citing selective restriction of ships carrying offensive weapons. In 1990, United Nations Security Council Resolution 661 imposed a trade embargo and sanctions against Iraq, due to which a Maritime Interception Force was created to enforce the embargo. It should, however, be remembered that an embargo is not an act of war and is sanctioned by multilateral treaties or the United Nations, while a blockade is an act of war governed by International Humanitarian Law as well as customary international law.

A blockade is imposed in response to an act of war during conflict or initiated as an act of war, satisfying conditions such as provision of access to humanitarian aid, proportionality, non-interference with neutral countries, official declaration, impartiality, and the use of assets for enforcement (a paper blockade without assets is not considered legal).

It is governed by a body of customary international law, including the 1856 Declaration of Paris, the London Declaration 1909, and the 1994 San Remo Manual. According to the San Remo Manual’s paragraphs 67(a), 93–104, 146(f) and 153(f), adopted on 12 June 1994, the territorial limits of the blockade have to be defined along with time limits to allow neutral ships to leave the blockaded zone.

International law regarding the sea has evolved significantly since the 1980s, when the United Nations Convention on the Law of the Sea was opened for signature on 10 December 1982 and entered into force in 1994. It has been signed and ratified by 168 states, while certain states, including Iran, have signed but not ratified it. The USA has also not ratified the treaty, along with a few other countries such as Turkey, Israel, Syria, Iran, Libya, Eritrea, and Venezuela. The right of innocent passage and the right of transit, as per UNCLOS, apply to the movement of any ship through an international waterway, including territorial waters of a country.

The right of innocent passage is codified in Articles 17–19 of UNCLOS and means movement “not prejudicial to the peace, good order, or security of the coastal states”. According to this, merchant vessels, civilian ships and warships can pass through the territorial waters of a state provided they do not violate the conditions enshrined in Articles 17–19 of UNCLOS. Submarines, however, are required to pass only while on the surface and with flags displayed.

The right of innocent passage for international navigation cannot be negated and is protected even by customary international law. Article 16(4) of the 1958 Convention on the Law of the Sea also supports the right of innocent passage of ships through territorial waters without prior authorisation, provided it meets the conditions of safety, and there is no hostile act or intent.

The right of transit passage applies to the movement of ships through waterways linking one part of the high seas with another, for example, the Strait of Hormuz, the Strait of Malacca and the Strait of Gibraltar. The right of transit passage, defined in Article 38 and Article 44 of UNCLOS, clearly states that there shall be no suspension of transit passage, even for security or any other reasons, according to some jurists.

Although the law of naval warfare permits interdiction of warships used for military purposes, this is not allowed for civilian ships. Iran had submitted a declaration while signing the Law of the Sea that it would only recognise the right of passage of ships of nations that had ratified the law. Even if this reasoning is conceded, there is another law based on the 1958 Convention (Article 16(4)) that grants the right of transit passage even to countries that have not ratified the Law of the Sea.

The International Court of Justice (ICJ) has ruled in the Corfu Channel case that British warships could exercise the right of innocent passage through the territorial waters of Albania, since the waterway was an international strait, i.e. a body of water that connects two high seas. The same analogy applies to the Strait of Hormuz, which Iran has blocked under its territorial waters rights.

It is worth highlighting that the shipping lanes in the Strait of Hormuz are primarily within Omani territorial waters, and Iran alone does not exercise territorial rights over those waters. The Iranian laying of sea mines also raises legal questions, as, despite permissibility under the law of naval warfare, certain conditions must be met while laying such mines.

Hormuz is not the cause but the effect of the present conflict and a very effective asymmetric tactic used by Iran to create supply chain disruption of oil, fertilisers, minerals and chemicals impacting the whole world

Hormuz is not the cause but the effect of the present conflict and a very effective asymmetric tactic used by Iran to create supply chain disruption of oil, fertilisers, minerals and chemicals impacting the whole world

These conditions include strict limitations on their use, including the prohibition of indiscriminate attack, the obligation to take precautions to protect civilian shipping, and the prohibition of blockade of international shipping lanes where no alternative navigation exists. Observing the geography of the Strait of Hormuz and the lack of alternatives for sea commerce, it becomes quite clear that meeting all of these conditions is extremely difficult in the Strait of Hormuz. Iran, therefore, does not have solid legal grounds for blocking an international waterway that guarantees the right of innocent passage as well as the right of transit passage, especially for civilian sea commerce, both under UNCLOS and customary international law.

There are countries such as Turkey that exercise special rights under specified conditions over international waterways like the Dardanelles and Bosphorus Straits under a special law enshrined in the Montreux Convention. The Montreux Convention was signed in 1936 to give certain rights to Turkey over shipping traffic in Turkish waters.

The Convention was signed due to peculiar geopolitical reasons, where the Allied powers were not keen to cede control of the waterway and associated territory to Russia. Turkey, according to the Montreux Convention of 1936, is therefore allowed to levy some fees besides imposing limits on tonnage and duration for non-Black Sea nations. There are certain limitations on submarine movement of non-Black Sea countries, and Article 35 of UNCLOS recognises the exception granted to Turkey under the Montreux Convention.

UNCLOS and customary international law govern sea commerce and transit through several important international waterways like the Straits of Malacca, Singapore and Gibraltar. If Iran’s control, including the right to levy toll tax on ships moving through the Strait of Hormuz during peacetime, is conceded, it would create a precedent that the international community would be loath to accept.

While it is understood that in an existential war of survival, Iran is using the closure of the Hormuz Strait as an asymmetric strategy, it should well understand the illegality of controlling or levying taxes on international shipping traffic, according to UNCLOS as well as customary international law. Iran could justify its blockade under the law of naval warfare, but only against belligerents that are fighting it, not neutral countries that are being adversely impacted by that blockade.

The American naval blockade of Iranian ports is also an act of war and is permitted only after meeting certain conditions defined by international law, i.e. official declaration, effectiveness (sufficient deployment of resources to ensure blockade), impartiality (applicability to all nations, including neutrals), limitation to enemy territory, and allowing humanitarian access.

The US blockade satisfies the above conditions except for humanitarian access, about which the information is opaque. While expressing willingness for a ceasefire and negotiations, the US has resorted to a blockade, which is an act of war. It is for US leadership to consider lifting the blockade for the duration of negotiations if the Iranians also reciprocate by opening the Strait of Hormuz in the interest of peace.

As negotiations cannot be conducted during active hostilities, similarly, peace agreements cannot be expected under blockades and counter-blockades. It is for both protagonists in the conflict equation to see the value of a negotiated end to hostilities, and the best confidence-building measure could be the suspension of both blockades by Iran and the USA concurrently. On the negotiating table, other weightier issues should take precedence over the post-war status of the Strait of Hormuz, which could be amicably resolved after the main contentious issues are settled.

Hormuz is not the cause but the effect of the present conflict and a very effective asymmetric tactic used by Iran to create supply chain disruption of oil, fertilisers, minerals and chemicals impacting the whole world. Leaving aside the legality or illegality of Iranian actions such as the blockade of Hormuz in wartime, one thing is certain: the issue of Hormuz closure is a subset of bigger issues, such as uranium enrichment and missile rights, which are being conflated with sovereignty by Iran and international security by the USA.

If a negotiated settlement of the ten contentious issues is achieved, the likelihood of the status of the Strait of Hormuz reverting to its pre-war status is high in light of the international community’s preference and the force of international law.

© The Friday Times