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Is Iran legally permitted to close Strait of Hormuz to countries that impose sanctions against Iran's oil?


By Bahman Aghai Diba, PhD International Law of the Sea

The Strait of Hormuz is the narrow sea passage that connects the Persian Gulf to the Oman Sea. This is the only sea-passage for the export of oil from the Persian Gulf states. (1) Recently, due to the revival of the possibility of new sanctions against the Islamic Republic of Iran, which may include sanctions against the purchase of oil and the sale of petroleum products to Iran, the issue of Iran’s reactions, especially the closure of the Strait of Hormuz, has turned into a hot topic. Some Iranian officials have recently claimed that according to the 1958 Geneva Convention on the Law of the Sea, Iran can suspend the passage from the Strait of Hormuz for the countries that impose sanctions against the Iranian oil and gas imports and exports. This is a piece on the legal, political, military and practical aspects of this issue.

Strait of Hormuz
(map from: )

The Government of the Islamic Republic of Iran has claimed time and again in the past that if it is put in serious danger it will close the Strait of Hormuz. Kayhan Newspaper, which is close to power circles in Iran, has reported in the past: “closing the Strait of Hormuz will seriously stop the flow of oil to the industrial states and they will face intolerable conditions.” (2)

Closing the Hormuz is going to be a two-sided weapon. Oil prices over a hundred dollars will have serious consequences for the international economy. However, Iran as an oil exporting country will be in a difficult situation if the export of oil is stopped. Iran's government derives about 80% of its revenues and most of its foreign currency from oil sales. Iran is not only relying on the oil revenues for its economy, but also it is an importer of oil products. Iran does not have the capacity to produce enough gasoline for internal consumption, and it has to import a major part of its needs from other countries.

However, the claims about closing the Strait of Hormuz, has several aspects:

Political Aspect
The Strait of Hormuz is the export channel for 40 percent of the oil production of the entire area. This means that closing the strait is a declaration of war to the other exporting countries (Saudi Arabia, Kuwait, Iraq, Qatar, UAE, and Bahrain) and also to the importing states (including Japan, and the Western states that depend heavily on the oil from the area).

Military Aspect
From military point of view, it requires great effort to close the strait, the narrowest part of which is 34 miles wide. The Iranian forces have conducted several maneuvers aimed at closing the Strait of Hormuz during a time of crisis, and the Western forces in the region (in cooperation with the some littoral countries or independently) have conducted several maneuvers aimed at deterring such plans. Although Iran may have enough firepower in the region to create problems, its military power is no match for the powerful forces present in the region. The military forces of the Persian Gulf littoral states have been increasing in the last several years, and at the moment, even a small country like the UAE has a more powerful air force than Iran. The American navy and other forces are heavily present in the region. In fact, in April 1988, US Navy, in retaliation against the mining of sea lanes by Iran (during the Tanker Wars), destroyed almost half of the Iranian navy in several hours in Operation Praying Mantis. (3) The French forces have a newly-established base in the area very close to the Strait of Hormuz and their main mission is to keep the Strait open.

Legal Aspect
It should be noted that any action by Iran to stop the flow of oil from Persian Gulf countries by blocking the strait Hormuz, attacking shipping lines, trying to blow up pipelines or the production and refinery facilities of the other countries in the region (such as Azerbaijan, Kazakhstan, and Turkmenistan in the Caspian Sea, or Saudi Arabia, Kuwait, Iraq, Qatar, the United Arab Emirates, Oman, Bahrain in the Persian Gulf), will be considered a serious violation of international laws and regulations for the concerned states. It would be in practice like giving them a declaration of war. At the same time, it would be a serious challenge to the interests of the major oil importing states, especially the USA.

Iran has signed the 1982 UN Convention on the Law of the Sea, but has not ratified it. However, Iran is committed to the convention (4), and considers the transit passage as only for those who have ratified it (US has not). So in the case of these countries Iran still believes in Innocent Passage. But innocent passage in the Straits used for international navigation is different.

One of the important subjects discussed during the various sessions of the UN Third Conference on the Law of the Sea was the regime of passage from the international straits such the Hormuz strait. The 1982 convention created and approved a new notion for passing from these straits which is called “transit passage”, and it gives more rights and freedoms to the passing ships than the previous customary regime of passage from these straits.

According to the declaration that Iran has issued at the time of signing the 1982 UN Convention on the Law of the Sea ,as far as the transit passage was concerned was that the new rights were based on the contract and therefore they extended only to those who accept all commitments coming from the 1982 convention, and that it did not extend to those who are not the members. The Iranian concern in this case, contrary to the well-known idea that it was against the big naval countries, was also coming from its conflicts with the Arab neighboring countries that tried to undermine the rights of coastal states of such waterways as much as possible. The Iran-Iraq- war (1980-1988) had added fuel to this kind of thinking.

During the Third UN Conference on the law of the Sea, the issue of passage from the international straits had gained special importance because:

  1. It was a matter of controversy between the countries bordering the straits and other countries especially the countries with big naval and merchant fleets.
  2. The practice of 12 mile territorial sea was recognized and supported by the countries and it added seriously to the number of international straits that were less than 24 miles and therefore entirely within the territorial limits of the bordering states.
  3. The previous customary regime of passage on the basis of 1958 convention of the territorial sea (Geneva Convention) was innocent passage. “Under the regime of innocent passage codified in Section III of the 1958 Geneva Convention, the rule is established that transit is innocent only “so long as it is not prejudicial to the peace, good order or security of the coastal state.” The last section of the article also requires that submarines exercising the right of innocent passage navigate on the surface, showing their flag. In Article 16 a coastal state is given the right to “take the necessary steps in its territorial sea to prevent passage which is not innocent.” This phraseology is nebulous enough as it stands; furthermore, the use of the word “prejudicial” suggests that an actual injury to peace, good order, or security need not be taking place for the passage to be deemed no longer innocent. If a reasonable chance exists that such injury may be in the offing, the coastal state would be in a strong position to decide that the passage is not innocent and exclude the vessel from its territorial waters.” (5)

The passage of the naval units from the territorial sea or in others words, extending the right of innocent passage to warships, was a controversial issue during the Third UN Conference on the Law of the Sea, and after the conclusion of the UNCLOS. The military issues were not in the agenda of the Third UN Conference on the Law of the Sea. However, during the sessions of the conference there were efforts to include subjects like the peaceful use of the oceans but they were not seriously followed. Therefore, the 1958 Convention on the territorial Sea and the 1982 UNCLOS have no clear regulations about the passage of the naval units from territorial seas. (6) Iran believes that the passage of naval ships of other states from territorial waters is dependent on prior notification and by observing innocent passage requirements. Some other countries that have the same policy are Egypt, Oman and Yemen.

Some Iranian politicians and academics have tried to argue that Iran has the right to close the Strait if the other countries ban its oil export and imports. One of them claims: “Iran believes that its likely enemies have to know that they do not possess all the chess pieces on the board. If Tehran is due to be deprived of its oil exports or faces paralyzing sanctions, the Strait of Hormuz will not be secure to tankers and ships carrying commercial goods or weapons to and from its enemies.” (7) The legal reason that Iran uses to substantiate its position is the Geneva Convention on the Territorial Sea and the Contiguous Zone (1958).

It should be noted that this argument has many problems, some of which are:

  1. Even if we accept that the regulations about “transit passage” as envisaged in the 1982 Law of the Sea convention, do not apply to the countries that have not joined it (this argument is rejected by many legal experts on the basis that the transit passage as mentioned the UN 1982 Convention has turned into a part of customary law and it is obligatory for all states, Iran has signed but not ratified the 1982 convention, and according to the law of treaties, it is under the commitment to refrain from doing anything contrary to it between the signature and ratification period), and the passage of ships from straits used for international navigation is not subject to the same kind of “innocent passage” that is mentioned in the 1958 Convention about the innocent passage from the territorial sea. The littoral states of straits used for international navigation do not have the right to suspend the innocent passage in such waterways.
  1. Most of the “traffic separations lines” (these are the lines usually used by the ships travelling in the area) are situated in the side of the Strait of Hormuz, which technically, i.e. according to the international law of sea, is part of Oman's territorial waters. The Iranian forces cannot make decisions for the other part of the Strait which is technically the territorial sea of Oman.

Notes and references:

  1. There are plans to establish a pipeline in the Arabian side of the Persian Gulf to bypass the Strait of Hormuz, but it is not ready, and when it is ready, it can’t replace the entire export capacity of the Arab oil exporting countries in the Persian Gulf region.
  2. Also, Ayatollah Ali Khamenei, Iran's Supreme Leader, has given a warning that Iran would disrupt the oil shipments in the Persian Gulf if the USA "makes a wrong move" in the confrontation with Iran over the nuclear program of Iran. (

    Also, in 2006, the Iranian oil Minister, Kazem Vaziri-Hamaneh, claimed that Iran may use the oil weapon, if such would serve its national interests. (, dated 27 June 2006).

    Also, the Iranian government spokesperson, Gholam-Hossein Elham said: "Iran would disrupt oil supplies as the last resort if it were punished over its nuclear program". (
  5. According to the article 18 of the convention on the law of treaties:
    “Obligation not to defeat the object and purpose of a treaty prior to its entry into force
    A State is obliged to refrain from acts which would defeat the object and purpose of a treaty when:
    (a) It has signed the treaty or has exchanged instruments constituting the treaty subject to
    Ratification, acceptance or approval, until it shall have made its intention clear not to become a party to the treaty; or
    (b) It has expressed its consent to be bound by the treaty, pending the entry into force of the treaty and provided that such entry into force is not unduly delayed.
  6. RWG De Muralt, the military aspects of the UN Law of the Sea Convention, Netherlands Law Review, 1985, Vol. XXXII.


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