By Argenis RODRIGUEZ (maritime lawyer)
In last couple of months, the Islamic Republic of Iran has closed the Strait of Hormuz by laying mines in its waters and charging a toll for crossing; all as part of a military strategy against the United States, which has responded with a blockade to prevent ships from going to and from Iran. All of this, as is evident, complicates the flow of international trade, especially that of hydrocarbons, and has the potential effect of increasing oil prices, as well as the cost of various goods and services.
Strait of Malacca: a strategic global chokepoint
This conflict has put the focus on another of the main chokepoints of world trade, which is the Strait of Malacca. Stretching about 805km between the Indonesian island of Sumatra and the Malay Peninsula, with Thailand to the north and Singapore at its southern entrance, it provides the shortest sea route between the Middle East and East Asia and carries more than a fifth of global maritime trade, being the world’s busiest chokepoint1.
It carries 45% of the world’s seaborne oil, over 25% of all cars traded internationally and 23% of dry bulk cargo including key agricultural commodities like grains and soybeans. The strait is also home to some of the world’s most critical port infrastructure. Singapore, located at the strait’s southern entrance, is the second-busiest container port and the busiest container transshipment hub on the planet2.
Legal framework and transit passage under UNCLOS
The Strait is the shortest sea route connecting the Indian Ocean to the South China Sea and Pacific Ocean, making it the default corridor for trade between East Asia and the West. It stretches roughly 900 kilometers from the Malay Peninsula to the Indonesian island of Sumatra.
At its narrowest point, the Phillips Channel near Singapore, it is barely 2.8 kilometers wide3.
Indonesia, Malaysia and Singapore border the strait and exercise sovereignty over their territorial waters, which can extend up to 12 nautical miles from their coastlines under the United Nations Convention on the Law of the Sea (UNCLOS). The three littoral States established a tripartite framework in 1971 to coordinate management of the strait4.
In the Strait of Malacca, the right of transit passage enshrined in UNCLOS applies, meaning that coastal States must allow the rapid and uninterrupted passage of ships and aircraft through the strait, and they have limited legislative and enforcement capabilities.
Rising tensions and political signals
For the time being, passage through the Strait of Malacca has not been interrupted in any way; however, the ongoing blockade of the Strait of Hormuz, and certain statements made in recent days, are raising concerns in the international community.
If global tensions rise, whether due to regional conflicts, naval disputes, or disruptions in other
routes like the Strait of Hormuz, the pressure on Malacca increases even further. This is because ships may get rerouted or face higher security risks, making the strait more congested and vulnerable5.
Indonesian Finance Minister Purbaya Yudhi Sadewa floated – and quickly walked back – the possibility of charging ships to transit the strait after Iran moved to do so in the Hormuz strait6.
UNCLOS expressly prohibits charging fees simply for passing through an international strait, but it is possible to charge fees for services provided to ships.
The idea of a Malacca toll has already been dismissed without qualification by Singapore, which has on several occasions declared that passage through the Strait of Malacca must remain free for all7. Malaysia has also emphasized the importance of maintaining unimpeded passage, reflecting a shared interest among littoral States in keeping traffic flowing8.
Whether or not Minister Purbaya was serious, the fact that a minister of the world’s fourth-most populated country is even willing to suggest the idea of charging a toll at the Malacca Strait is an example of how the erosion of an international norm can quickly cascade throughout the international system9.
Additionally, the Indonesian Defense Ministry is also weighing a US proposal for military aircraft overflight access through Indonesian airspace, something that drew significant pushback within its own military establishment, including over sovereignty concerns10.
Despite all of the above, the Strait of Malacca will apparently remain open for the transit of ships and aircraft; however, there is a “tense calm”.
Iran’s illegal closure of the Strait of Hormuz already constitutes a dangerous precedent that, if maintained for a long time, other coastal States with geographic leverage may draw the same conclusion that the oceans are not a commons to be maintained but an asset to be monetised11.
Is transit passage really a binding international norm?
A hypothetical closure of the Strait of Malacca, or the imposition of tolls for passage through it, would seriously jeopardize freedom of navigation as we currently know it, since the right of transit passage through international straits does not appear to be part of customary international law, despite the United States maintaining the position that this right is binding on all States. Indeed, as made clear in the closing statement by the President of the Third United Nations Conference on Law of the Sea:
“The argument that, except for Part XI, the Convention [LOSC] codifies customary law or reflects existing international practice is factually incorrect and legally insupportable. The regime of transit passage through straits used for international navigation and the regime of archipelagic sea lanes passage are only two examples of the many new concepts in the Convention”
Despite the great importance of the right of transit passage to maintain the flow of international trade, its status as part of customary international law has always been in doubt, which is why Iran believes it has the right to close the Strait of Hormuz as it sees fit.
As already stated, if passage through the Strait of Hormuz is not resumed in the short term, and if passage through other chokepoints is intentionally obstructed by coastal States, such as the Strait of Malacca or Bab-el-Mandeb, this will undermine the right of transit passage and weaken the United States’ position that this right is binding on all States, which could lead to the forced reshaping of the maritime routes of international trade.
What’s at stake for global trade and consumers?
Because of this delicate situation, the importance of Singapore and Malaysia defending free transit through the Strait of Malacca cannot be underestimated, since if maritime routes are altered due to current geopolitical tensions, the biggest losers in this situation would not be the large shipping and exporting companies, but the ordinary citizen who buys the products that are traded globally.
- The Straits Times. Why anxieties are rising over the Malacca Strait, Asia’s key shipping route. Accessed on May 4, Available: https://www.straitstimes.com/asia/se-asia/why-anxieties-are-rising-over-the-malacca-strait-asias-key-shipping-route ↩︎
- Asia Times. Strait of Malacca could be next Hormuz-like flashpoint. Accessed on May 4, 2026. Available:
https://asiatimes.com/2026/04/strait-of-malacca-could-be-next-hormuz-like-flashpoint/ ↩︎ - Ibid. ↩︎
- The Straits Times. Why anxieties are rising over the Malacca Strait, Asia’s key shipping route. Accessed on May 4, 2026. ↩︎
- The Sunday Guardian. What is China’s ‘Malacca Dilemma’? Why the Strait of Malacca is Becoming One of the World’s Most Critical Chokepoints After the Strait of Hormuz | Explained. Accessed on May 4, 2026. Available: https://sundayguardianlive.com/world/what-is-china-malacca-dilemma-why-the-strait-of-malacca-is-becoming-one-of-the-worlds-most-critical-chokepoints-after-the-strait-of-hormuz-explained-187907/ ↩︎
- The Straits Times. Why anxieties are rising over the Malacca Strait, Asia’s key shipping route. Accessed on May 4, 2026. ↩︎
- The Diplomat. Indonesian Finance Minister Raises Possibility of Imposing Toll on Strait of Malacca. Accessed on May 4, 2026. Available: https://thediplomat.com/2026/04/indonesian-finance-minister-raises-possibility-of-imposing-toll-on-strait-of-malacca/o ↩︎
- The Straits Times. Why anxieties are rising over the Malacca Strait, Asia’s key shipping route. Accessed on May 4, 2026. ↩︎
- The Diplomat. Indonesian Finance Minister Raises Possibility of Imposing Toll on Strait of Malacca. Accessed on May 4, 2026. ↩︎
- The Straits Times. Why anxieties are rising over the Malacca Strait, Asia’s key shipping route. Accessed on May 4, 2026. ↩︎
- Euractiv. Free passage is fading: Europe needs a navy. Accessed on May 4, 2026. Available:
https://www.euractiv.com/opinion/free-passage-is-fading-europe-needs-a-navy/ ↩︎
