Maritime conventions and international precedents impose restrictions on the closure of the strategic global oil trade route
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The Strait of Hormuz occupies a central geopolitical position. A significant portion of world trade in oil, fuels and fertilizers passes through it. Therefore, any threat to navigation has immediate repercussions on a global scale, as the entire world has been following. Therefore, international law establishes clear limits as to what can or cannot be done in this type of maritime space.
LEGAL REGIME OF INTERNATIONAL STRAITS
The legal regime applicable to the sea and, by extension, to navigation in the straits, is codified in the United Nations Convention on the Law of the Sea, also known as . Under the terms of , this regime applies “to straits used for international navigation between one part of the high seas or an exclusive economic zone and another part of the high seas or an exclusive economic zone”.
The Strait of Hormuz falls into this category, as it connects high seas areas or exclusive economic zones, linking the Persian Gulf to the Gulf of Oman. This qualification entails the application of a specific legal regime, called transit passage, provided for in .
This regime guarantees all ships and aircraft the right to cross the strait continuously and quickly, without the need for prior authorization, covering both civil and military vessels. The reference to “all ships and aircraft”in light of the structure of the Convention, covers both civil vessels and military ships. Coastal countries in the region cannot prevent or suspend transit passage.
The Montego Bay Convention provides that these countries “they will not impede transit passage and will give due publicity to any danger of which they are aware that threatens navigation in the strait or flying over it. [E que, além disso]there will be no suspension of the transit ticket”. The reference to “no suspension” can be interpreted as the consecration of an obligation whose applicability even extends to situations of conflict or international tension. Now, the robust nature of transit passage does not eliminate the existence of duties for ships.
REGULATORY CONTENT OF THE TRANSIT TICKET
The same convention establishes that ships must refrain from activities that are not directly related to transit. This includes, in particular, the prohibition of the use or threat of force, the duty to respect the sovereignty and territorial integrity of riparian States, as well as the prohibition of acts of pollution. Between the obligations of coastal States and those of ships, a balance is thus formed that is characteristic of contemporary law of the sea: access to the strait is largely guaranteed, but its use must remain strictly linked to the purpose of circulation.
IRAN’S NON-RATIFICATION OF UNCLOS
A central legal issue lies in the fact that the Montego Bay Convention. At first glance, this could suggest that the country would not be legally bound by the aforementioned rules. However, this conclusion does not hold up against the structure of contemporary international law.
Several provisions of the Convention, especially those relating to the straits, are now considered to be an expression of customary international law. This means that its obligation does not arise only from formal consent through treaties, but from a widespread habitual practice of States, accompanied by the conviction of its legal obligation. Therefore, Iran has an obligation to respect the legal regime that governs the straits.
THE “CONSUETUDINARY NATURE” OF THE NARROW REGIME
In 1949, the International Court of Justice itself, in the case of the Corfu channel, had already recognized the existence of a right of passage in international straits even before the adoption of the Montego Bay Convention, reinforcing the customary, that is, habitual, nature of this regime. An international custom can be challenged in practice. In this case, the objecting state is called a persistent objector.
The possibility of Iran invoking the status of persistent objector to exempt itself from these rules faces serious difficulties. For such an argument to be accepted, it would be necessary to demonstrate clear, consistent and continuous opposition since the formation of the customary norm.
There is no evidence that Iran has maintained a position of this nature over time, nor that it has managed to prevent the consolidation of a practice widely accepted by the international community. On the contrary, the repeated use of the strait by ships of different flags and the absence of a systematic and effective Iranian challenge significantly weaken this thesis.
It is true, however, that, in the case of the Corfu Canal, the International Court of Justice recognized the habitual nature of the right of passage, specifying its applicability in times of peace. In a context of war, the question arises as to whether a possible blockade of the strait could be justified on the basis of the right to self-defense.
LIMITS OF LEGITIMATE DEFENSE IN THE BLOCKADE OF STRAITS
Article 51 recognizes that States may react to an armed attack, as long as the requirements of necessity and proportionality are respected. The armed attack against Iran took place.
However, applying these criteria to a case like the Strait of Hormuz reveals important limitations. A generalized blockade affects not only the opposing state, but all users of the strait, including third states that do not participate in the conflict. This raises serious doubts regarding compliance with the necessity requirement, as less comprehensive measures, aimed exclusively at the belligerents, could, in principle, be adopted to respond to a specific attack.
Furthermore, the proportionality of a measure with such a significant global impact would be difficult to sustain. Closing the strait entails economic and strategic consequences that go far beyond the objective of repelling immediate aggression.
Added to this is the fact that such a measure would be in direct tension with the prohibition, enshrined in article 44 of the Convention, on impeding passage in transit. It is no coincidence that the blockade of the Strait of Hormuz has already been equated to the effects of an economic nuclear bomb.
