The major maritime straits have played a decisive role in international trade since the Modern Age and continue to be one of the main arenas of global geopolitical competition.
Law of the Sea
Geographer Sylvain Domergue, a lecturer at the Institute of Political Studies in Bordeaux and author of La géopolitique des domaines maritimes (2025), explains that the legal framework governing these natural corridors is based on the United Nations Convention on the Law of the Sea, known as the Montego Bay Convention.
This situation contrasts with that of man-made infrastructure such as the Suez and Panama Canals, which are managed by the states that administer them and are authorised to charge fees for the transit of vessels.
A cargo ship passing through the Suez Canal – PHOTO/ARCHIVE
Although Iran has never formally ratified the Convention, Domergue points out that Tehran has traditionally respected many of its provisions, regarding them as part of customary international law. However, the outbreak of conflict following the air strikes launched by the United States and Israel on 28 February upset this balance.
Iran’s decision to close the Strait of Hormuz – through which, under normal circumstances, around 20 per cent of the world’s oil and liquefied natural gas trade passes – triggered an immediate reaction in the energy markets, with a sharp rise in crude oil prices, whilst Washington responded with a naval blockade of Iranian ports.
Subsequently, a memorandum of understanding signed between Washington and Tehran in April allowed shipping to resume temporarily. However, the breakdown of the ceasefire in early July once again jeopardised maritime traffic through this strategic corridor.
Bab el-Mandeb and the Houthis
Regional instability also threatens another of the main chokepoints for global trade: the Strait of Bab el-Mandeb. Warnings from Yemen’s Houthi rebels about possible attacks on traffic bound for Saudi ports have reignited concerns over a disruption to access to the Suez Canal, a vital route for international transport of goods.
Oil tankers, LNG carriers, cargo ships and vessels transporting strategic goods for the global economy pass through the Strait of Hormuz and the Bab el-Mandeb Strait. Their importance, however, is not a recent phenomenon. Domergue recalls that Portugal sought to control the Strait of Hormuz from the early 16th century onwards to secure the sea route to India and consolidate its dominance over the lucrative spice trade.
A satellite image shows the Bab el-Mandeb Strait, a key shipping lane and the gateway to the Red Sea, as Iran threatens to use its Houthi allies in Yemen to block the passage through Bab el-Mandeb to the Red Sea, in this photograph provided and dated 12 July 2026 – NASA Worldview/Image via REUTERS
Mare Liberum
During the 17th century, a new legal concept emerged, championed by the Dutch jurist Hugo Grotius, who formulated the doctrine of Mare Liberum, based on the principle that the seas could not be subject to exclusive appropriation by any state.
This idea was first adopted by the Netherlands, later by England and, subsequently, by the United States, which, despite not having ratified the Montego Bay Convention, continues to apply many of its principles.
However, the defence of freedom of navigation did not prevent the great powers from using these enclaves to strengthen their strategic influence. The British Empire developed an extensive network of military bases situated around the major maritime straits.
Among these, Singapore stood out, having become the principal British naval base in Asia and a key element in controlling the Strait of Malacca, one of the busiest trade routes on the planet and vital for exports from China.
London also maintained a presence on the island of Socotra, situated at the entrance to the Red Sea and close to Bab el-Mandeb, with the aim of securing control of another of the main routes of communication between Europe and Asia.
The oil tanker Cordelia Moon bursts into flames after being hit by a missile in the Red Sea, off the port of Hodeida in Yemen, in this screenshot from a video published on 1 October 2024 – PHOTO/HOUTHI MILITARY MEDIA via REUTERS
On the European continent, the Danish straits played a comparable role for centuries by enabling Denmark to levy a toll on ships entering the Baltic Sea. At present, the Bosphorus and the Dardanelles constitute an exception within the general regime governing international straits, as transit through them continues to be regulated by the 1936 Montreux Convention, which establishes a specific regime for navigation through both waterways.
Domergue anticipates that new problems relating to straits will arise in the future, highlighting in particular the Taiwan Strait in light of China’s regional ambitions, as well as the Strait of Malacca, which is under the joint supervision of Singapore, Malaysia and Indonesia.