An Overview of International Straits in Light of the Strait of Hormuz Crisis

Dr Inas Mohamed Ahmed

International straits constitute strategic maritime corridors for global shipping. They are generally defined as narrow waterways connecting two parts of the high seas or exclusive economic zones (EEZs). Under international law, a strait is regarded as such if its width does not exceed twice the breadth of the territorial sea of the coastal state or states bordering it. If it exceeds that limit, the legal regime of the high seas applies. A qualifying international strait must also be a naturally occurring waterway—not one created artificially—that separates two land masses and connects two bodies of water. These are the principal characteristics of an international strait.

International law first addressed the legal status of straits through the 1958 Geneva Convention. Still, the modern regulation of international straits can be traced back to 22 October 1946, when British warships struck naval mines while passing through the Corfu Strait, which lies within Albanian territorial waters. The explosions caused extensive casualties, killing approximately 44 British sailors and inflicting serious damage on the vessels.

As a consequence, the United Nations Security Council, through Resolution 22 of 9 April 1947, referred the dispute to the International Court of Justice (ICJ). On 22 May 1947, the United Kingdom instituted proceedings against Albania without prior negotiations, alleging that Albania had laid the mines in violation of freedom of navigation and the right of innocent passage.

The Corfu Channel Case became the first dispute ever heard by the International Court of Justice following its establishment. The Court delivered its judgments in several stages. In 1948, it affirmed its jurisdiction to hear the dispute. In 1949, it held Albania internationally responsible for the mines while reaffirming that the right of innocent passage must not be obstructed or denied by coastal states.

The Court also ordered Albania to pay financial compensation to the United Kingdom for the loss of life and material damage suffered. This remains the only case in which the International Court of Justice has awarded monetary compensation directly to an injured state.

The Corfu Channel Case established two fundamental principles: that innocent passage does not require prior authorisation, and that vessels exercising this right must not be exposed to hazards or harm.

This case paved the way for the codification of the law of the sea. The 1958 Geneva Convention on the Territorial Sea and the Contiguous Zone introduced another important principle through Article 16(4): innocent passage through international straits may not be suspended. Nevertheless, the Convention remained limited in scope.

Subsequently came the negotiations of the Third United Nations Conference on the Law of the Sea (1973–1982), culminating in the United Nations Convention on the Law of the Sea (UNCLOS) 1982, which entered into force in 1994.

UNCLOS introduced the concept of transit passage, granting broader navigation and overflight rights through international straits. Transit passage is defined as “the exercise of the freedom of navigation and overflight solely for continuous and expeditious transit through the strait.”

Transit passage differs from innocent passage in several significant respects:

Transit passage permits both civilian and military aircraft to overfly the strait, whereas innocent passage does not allow aircraft to fly over the territorial sea.

Under transit passage, submarines may navigate while remaining submerged. By contrast, innocent passage requires submarines to navigate on the surface and display their national flag.

Both legal regimes prohibit the suspension of passage. However, coastal states exercise broader regulatory authority under innocent passage than under transit passage. Transit passage must be continuous and expeditious, without unnecessary delay, and vessels and aircraft must refrain from any threat or use of force that would endanger the sovereignty, territorial integrity, or security of the coastal states.

The 1982 United Nations Convention on the Law of the Sea has been ratified by the vast majority of states, including eighteen Arab countries. However, some states—including the Islamic Republic of Iran, the United States, and Israel—have not become parties to the Convention.

Even so, these states remain bound by the customary rules of international law reflected in UNCLOS, particularly the principle of freedom of navigation. International law also recognises the right of coastal states to designate shipping lanes and establish traffic separation schemes.

Applying these principles to the Strait of Hormuz, which has become a focal point of tensions during the US-Iran confrontation, reveals a particularly complex application of the transit passage regime.

At its narrowest point, the Strait measures approximately 21 nautical miles across, placing it entirely within the territorial seas of Iran and the Sultanate of Oman. Between 35 and 37 per cent of globally seaborne oil passes through the Strait, making it one of the world’s busiest commercial maritime corridors.

Consequently, any instability in the Strait has serious repercussions for global energy supplies and industrial production.

Under Article 44 of UNCLOS, which provides that “there shall be no suspension of transit passage,” any attempt by Iran to impose fees or unjustified restrictions on transit would constitute a breach of international law.

However, practical realities are more nuanced. As a coastal state, Iran enjoys certain powers under Article 42(a) and (b) of UNCLOS to adopt laws relating to the prevention of pollution and the protection of its national security. It may therefore introduce measures designed to safeguard its security and maritime safety.

Accordingly, the application of the law itself may, in certain circumstances, require further clarification.

A similar issue arises when nuclear-powered vessels or ships carrying hazardous cargo pass through narrow international straits. Coastal states may reasonably seek prior notification to adopt precautionary measures to protect their territory and waters from potential environmental contamination.

The difficulty, however, is that UNCLOS does not distinguish among categories of vessels by the nature of their cargo when regulating transit passage.

This highlights the growing need for enhanced mechanisms of international cooperation, since any disruption in these strategic waterways affects the entire global community.

At the same time, the law of the sea remains one of the most flexible branches of international law, particularly regarding dispute settlement. It has successfully balanced the interests of states exercising international navigation and overflight rights under transit passage with those of coastal states seeking to safeguard their sovereignty and security.

Its overriding principle nevertheless remains clear: transit passage may not be suspended under any circumstances.

Anyone observing contemporary tensions surrounding international straits—whether the confrontation between Iran and the United States near the Strait of Hormuz, the instability around the Bab el-Mandeb Strait, which has disrupted maritime traffic, the continuing diplomatic disputes between Spain and the United Kingdom over the administration of Gibraltar, the only natural gateway linking the Mediterranean Sea with the Atlantic Ocean and a strategic control point for NATO, as well as a key route for American military aircraft travelling to the Middle East, or the Strait of Malacca, connecting Indonesia, Malaysia, and Singapore, and linking the Pacific and Indian Oceans while serving as the economic and energy lifeline for countries such as China, Japan, and South Korea—cannot fail to recognise that these strategic waterways require a fundamental rethinking of international policy.

The real challenge today lies in the absence of modern mechanisms for international cooperation and robust legal frameworks capable of preventing international straits from becoming instruments of geopolitical competition—whether through exploitation by coastal states or by major powers—and from being used as tools of economic or military coercion to threaten global trade, energy security, or industrial production under any circumstances.

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