Interesting look at the legalities of transiting the Strait of Hormuz traffic lanes by Kaveh L. Afrasiabi here:
Tension spiked markedly last week when Iranian Revolutionary Guards Corps (IRGC) speedboats were involved in an "incident" with three US Navy vessels, which claimed they were international waters.The issue is one of sovereignty, akin to those discussed here previously with respect to the Strait of Malacca (see here, here, and here, as examples).
Yet there is no "international water" in the Strait of Hormuz, straddled between the territorial waters of Iran and Oman. The US government claimed, through a Pentagon spokesperson, Bryan Whitman, that the three US ships "transiting through the Strait of Hormuz" were provocatively harassed by the speedboats. This was followed by the Pentagon's release of a videotape of the encounter, where in response to Iran's request for ship identification, we hear a dispatch from one of the US ships stating the ship's number and adding that "we are in international waters and we intend no harm".
Thus there is the issue of the exact whereabouts of the US ships at the time of the standoff with the Iranian boats manned by the IRGC patrolling the area. According to Vice Admiral Kevin Cosgiff, the US ships were "five kilometers outside Iranian territorial waters". Yet, this is disputed by another dispatch from the US ships that states, "I am engaged in transit passage in accordance with international law."
Given that the approximately three-kilometer-wide inbound traffic lane in the Strait of Hormuz is within Iran's territorial water, the US Navy's invocation of "transit passage" harking back to the 1982 UN Convention on the Law of the Sea, (UNCLOS) is hardly surprising. 
However, irrespective of how Congress acts on the pending legislation on UNCLOS, the fact is that the US cannot have its cake and eat it. That is, rely on it to defend its navigational rights in the Strait of Hormuz and, simultaneously, disregard the various limitations on those rights imposed by the UNCLOS - and favoring Iran. These include the following:
- Per Article 39 of the UNCLOS, pertaining to "duties of ships during transit passage" US ships passaging through the Strait of Hormuz must "proceed without delay" and "refrain from any threat or use of force against the sovereignty, territorial integrity or political independence of states bordering the strait".
- Per Article 40, "During transit passage, foreign ships may not carry out any research or survey activity without the prior authorization of the states bordering the straits." And yet, by the US Navy's own admission, it has been conducting sonar activities in the area, to detect submerged vessels. This, in turn, has harmed the Persian Gulf's aquatic mammals. In light of a recent US court ruling limiting the US Navy's sonar activities off the California coast, Iran now has greater political leverage to seek information regarding the activities of US warships transiting through its territorial waters.
- Given the US's verbal acrobatics, of trying to depict as "international waters" what is essentially Iran's territorial water in the inbound traffic channel of the Strait of Hormuz, it collides with Article 34 of UNCLOS. This regards the "legal status of waters forming the straits used for international navigation", that strictly stipulates that the regime of passage "shall not affect the legal status of the waters forming such straits". Following the UNCLOS, Iran's territorial water extends 12 nautical miles at the Strait of Hormuz.
- The Pentagon videotape of the incident shows a US helicopter hovering above the US ships, which is in clear contradiction of Article 19 of the UNCLOS, which expressly forbids "the launching, landing or taking on board of any aircraft" during transit passage.
- Article 19, elaborating on the meaning of "innocent passage", states that "passage is innocent so long as it is not prejudicial to the peace, good order or security of the coastal state". And that means a prohibition on "any exercise or practice with weapons of any kind" and or "any act of harmful and serious pollution".
In other words, US warships transiting through Hormuz must, in effect, act as non-war ships, "temporarily depriving themselves of their armed might". And any "warning shots" fired by US ships at Iranian boats, inspecting the US ships under customary international laws, must be considered an infringement on Iran's rights. This technically warrants a legal backlash in the form of the Iranians temporary suspending the US warships' right of passage. Again, the US could be technically prosecuted by Iran in international forums for conducting questionable activities while in Iranian territorial waters.
- Under Article 25 of the UNCLOS, a "coastal state may take the necessary steps in its territorial sea to prevent passage which is not innocent ... the coastal state may suspend temporarily in specified areas of its territorial sea the innocent passage of foreign ships if such suspension is essential for the protection of its of security, including weapons exercise."
- Per Article 30, "If any warship does not comply with the laws and regulations of the coastal state concerning passage through the territorial sea and disregards any request for compliance therewith which is made to it, the coastal state may require it to leave the territorial sea immediately."
- Pursuant to Article 42 of the UNCLOS, "states bordering straits may adopt laws and regulations relating to transit passage" and "foreign ships exercising the right of transit passage shall comply with such laws and regulations." In this connection, Iran's 1993 maritime law echoes Article 20 of the UNCLOS: "In the territorial sea, submarines and other underwater vehicles are required to navigate on surface and to show their flag." Yet, disregarding both international law and Iran's laws, the US Navy until now has refused to comply with the requirement of surface passage of its submarines through the Strait of Hormuz.
The UNCLOS provisions that may apply:
Article34Of course, there are also obligations imposed on the bordering state:
Legal status of waters forming straits used for international navigation
1. The regime of passage through straits used for international navigation established in this Part shall not in other respects affect the legal status of the waters forming such straits or the exercise by the States bordering the straits of their sovereignty or jurisdiction over such waters and their air space, bed and subsoil.
2. The sovereignty or jurisdiction of the States bordering the straits is exercised subject to this Part and to other rules of international law.
Scope of this Part
Nothing in this Part affects:
(a) any areas of internal waters within a strait, except where the establishment of a straight baseline in accordance with the method set forth in article 7 has the effect of enclosing as internal waters areas which had not previously been considered as such;
(b) the legal status of the waters beyond the territorial seas of States bordering straits as exclusive economic zones or high seas; or
(c) the legal regime in straits in which passage is regulated in whole or in part by long-standing international conventions in force specifically relating to such straits.
High seas routes or routes through exclusive economic zones through straits used for international navigation
This Part does not apply to a strait used for international navigation if there exists through the strait a route through the high seas or through an exclusive economic zone of similar convenience with respect to navigational and hydrographical characteristics; in such routes, the other relevant Parts of this Convention, including the provisions regarding the freedoms of navigation and overflight, apply.
SECTION 2. TRANSIT PASSAGE
Scope of this section
This section applies to straits which are 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.
Right of transit passage
1. In straits referred to in article 37, all ships and aircraft enjoy the right of transit passage, which shall not be impeded; except that, if the strait is formed by an island of a State bordering the strait and its mainland, transit passage shall not apply if there exists seaward of the island a route through the high seas or through an exclusive economic zone of similar convenience with respect to navigational and hydrographical characteristics.
2. Transit passage means the exercise in accordance with this Part of the freedom of navigation and overflight solely for the purpose of continuous and expeditious transit of the strait between one part of the high seas or an exclusive economic zone and another part of the high seas or an exclusive economic zone. However, the requirement of continuous and expeditious transit does not preclude passage through the strait for the purpose of entering, leaving or returning from a State bordering the strait, subject to the conditions of entry to that State.
3. Any activity which is not an exercise of the right of transit passage through a strait remains subject to the other applicable provisions of this Convention.
Duties of ships and aircraft during transit passage
1. Ships and aircraft, while exercising the right of transit passage, shall:
(a) proceed without delay through or over the strait;
(b) refrain from any threat or use of force against the sovereignty, territorial integrity or political independence of States bordering the strait, or in any other manner in violation of the principles of international law embodied in the Charter of the United Nations;
(c) refrain from any activities other than those incident to their normal modes of continuous and expeditious transit unless rendered necessary by force majeure or by distress;
(d) comply with other relevant provisions of this Part.
2. Ships in transit passage shall:
(a) comply with generally accepted international regulations, procedures and practices for safety at sea, including the International Regulations for Preventing Collisions at Sea;
(b) comply with generally accepted international regulations, procedures and practices for the prevention, reduction and control of pollution from ships.
3. Aircraft in transit passage shall:
(a) observe the Rules of the Air established by the International Civil Aviation Organization as they apply to civil aircraft; state aircraft will normally comply with such safety measures and will at all times operate with due regard for the safety of navigation;
(b) at all times monitor the radio frequency assigned by the competent internationally designated air traffic control authority or the appropriate international distress radio frequency.
Research and survey activities
During transit passage, foreign ships, including marine scientific research and hydrographic survey ships, may not carry out any research or survey activities without the prior authorization of the States bordering straits.
Sea lanes and traffic separation schemes in straits used for international navigation
1. In conformity with this Part, States bordering straits may designate sea lanes and prescribe traffic separation schemes for navigation in straits where necessary to promote the safe passage of ships.
2. Such States may, when circumstances require, and after giving due publicity thereto, substitute other sea lanes or traffic separation schemes for any sea lanes or traffic separation schemes previously designated or prescribed by them.
3. Such sea lanes and traffic separation schemes shall conform to generally accepted international regulations.
4. Before designating or substituting sea lanes or prescribing or substituting traffic separation schemes, States bordering straits shall refer proposals to the competent international organization with a view to their adoption. The organization may adopt only such sea lanes and traffic separation schemes as may be agreed with the States bordering the straits, after which the States may designate, prescribe or substitute them.
5. In respect of a strait where sea lanes or traffic separation schemes through the waters of two or more States bordering the strait are being proposed, the States concerned shall cooperate in formulating proposals in consultation with the competent international organization.
6. States bordering straits shall clearly indicate all sea lanes and traffic separation schemes designated or prescribed by them on charts to which due publicity shall be given.
7. Ships in transit passage shall respect applicable sea lanes and traffic separation schemes established in accordance with this article.
Laws and regulations of States bordering straits
relating to transit passage
1. Subject to the provisions of this section, States bordering straits may adopt laws and regulations relating to transit passage through straits, in respect of all or any of the following:
(a) the safety of navigation and the regulation of maritime traffic, as provided in article 41;
(b) the prevention, reduction and control of pollution, by giving effect to applicable international regulations regarding the discharge of oil, oily wastes and other noxious substances in the strait;
(c) with respect to fishing vessels, the prevention of fishing, including the stowage of fishing gear;
(d) the loading or unloading of any commodity, currency or person in contravention of the customs, fiscal, immigration or sanitary laws and regulations of States bordering straits.
2. Such laws and regulations shall not discriminate in form or in fact among foreign ships or in their application have the practical effect of denying, hampering or impairing the right of transit passage as defined in this section.
3. States bordering straits shall give due publicity to all such laws and regulations.
4. Foreign ships exercising the right of transit passage shall comply with such laws and regulations.
5. The flag State of a ship or the State of registry of an aircraft entitled to sovereign immunity which acts in a manner contrary to such laws and regulations or other provisions of this Part shall bear international responsibility for any loss or damage which results to States bordering straits.
Duties of the coastal State
1. The coastal State shall not hamper the innocent passage of foreign ships through the territorial sea except in accordance with this Convention. In particular, in the application of this Convention or of any laws or regulations adopted in conformity with this Convention, the coastal State shall not:
(a) impose requirements on foreign ships which have the practical effect of denying or impairing the right of innocent passage; or
(b) discriminate in form or in fact against the ships of any State or against ships carrying cargoes to, from or on behalf of any State.
2. The coastal State shall give appropriate publicity to any danger to navigation, of which it has knowledge, within its territorial sea.