TENSIONS ACROSS THE STRAIT OF HORMUZ: MAPPING THE INTERNATIONAL LAW INVOLVED
Author: Shruti Chaudhary
Introduction
The Strait of Hormuz occupies a unique position in international affairs. It is both one of the world's most important maritime routes and a focal point of recurring geopolitical tension. As the principal gateway connecting the Persian Gulf to the Gulf of Oman and the Arabian Sea, it facilitates the movement of a substantial proportion of global energy exports. Any disruption to navigation through the Strait has immediate implications not only for regional security but also for international trade and energy markets.
From a legal perspective, the Strait of Hormuz is more than a strategic chokepoint. It is classified under international law as a strait used for international navigation. This designation is significant because it subjects the waterway to a specific legal framework that limits the extent to which coastal states may interfere with maritime traffic. Consequently, debates surrounding tanker seizures, military deployments, sanctions enforcement, and threats to close the Strait must be assessed against established rules of international law.
The principal legal regimes governing tensions in the Hormuz Strait include the United Nations Convention on the Law of the Sea (UNCLOS), the United Nations (UN) Charter, the law of state responsibility, and various international maritime safety conventions. Together, these bodies of law seek to balance coastal-state sovereignty, freedom of navigation, and international security.
The Strategic and Legal Significance of the Strait
The Strait of Hormuz serves as the only maritime outlet for many Gulf states and is therefore indispensable to international commerce. Legally, its importance stems from its classification under Part III of UNCLOS as a strait used for international navigation connecting one part of the exclusive economic zone or high seas to another.
This classification has significant legal implications. Unlike ordinary territorial waters, which are generally subject to the regime of innocent passage, the Strait of Hormuz is primarily governed by the regime of transit passage. Under this framework, foreign vessels and aircraft enjoy more extensive rights of navigation and overflight, while the authority of coastal states to impede, restrict, or regulate movement through the strait is considerably limited.
Consequently, the legal framework applicable to the Strait is formulated to ensure that international navigation remains uninterrupted despite political disagreements or security concerns involving coastal states.
UNCLOS and the Regime of Transit Passage
The most important legal provisions governing the Strait of Hormuz are found in Articles 37 to 44 of UNCLOS.
Article 37 provides that the regime of transit passage applies to straits used for international navigation that connect one part of the high seas or an exclusive economic zone (EEZ) to another. The Strait of Hormuz clearly satisfies these criteria, as it serves as a vital international waterway linking the Persian Gulf with the Gulf of Oman and the wider high seas. Consequently, it falls within the scope of the transit passage regime established under the Convention.
Article 38 confers upon all ships and aircrafts the right of transit passage and expressly provides that this right must not be obstructed. It defines transit passage as the exercise of freedom of navigation and overflight solely for the purpose of continuous and expeditious movement through an international strait. As a result, merchant vessels, warships, and aircraft are entitled to pass through the Strait without the need to obtain prior permission or authorization from the coastal states bordering it.
However, these rights are accompanied by obligations. Article 39 imposes certain obligations on ships and aircraft exercising the right of transit passage. They are required to move through the strait without undue delay, adhere to internationally recognized standards relating to navigational safety and environmental protection, and refrain from any threat or use of force against the sovereignty, territorial integrity, or political independence of states bordering the strait. Thus, the provision reinforces the connection between the law of the sea and the fundamental principles embodied in the UN Charter.
Thus, UNCLOS acknowledges the legitimate interests of coastal states in regulating activities within their adjacent waters. Under Articles 41 and 42, states bordering international straits may designate sea lanes, establish traffic separation schemes, and enact laws concerning maritime safety, environmental protection, customs, immigration, and related matters. However, these regulatory powers are not unlimited. Any measures adopted must be applied on a non-discriminatory basis and must not interfere with, restrict, or effectively undermine the exercise of transit passage.
The most significant provision is Article 44, which obliges states bordering international straits to ensure that transit passage is not impeded and explicitly prohibits its suspension under any circumstances. This provision serves as a key legal basis for opposing any effort to block, restrict, or close the Strait of Hormuz to international navigation.
Transit Passage and Innocent Passage: An Important Distinction
Public discussions often conflate transit passage with innocent passage, but the distinction is crucial.
Innocent passage generally applies within a state's territorial sea and permits coastal states greater authority to regulate foreign vessels. Passage must remain "innocent," meaning it cannot threaten the peace, security, or good order of the coastal state.
Conversely, the regime of transit passage affords more extensive navigational freedoms. Designed specifically for straits used in international navigation, it guarantees passage rights to both vessels and aircraft and does not permit suspension by coastal states. While ships and aircraft must comply with certain legal obligations during transit, the authority of coastal states to regulate or obstruct movement through the strait is considerably more limited than under other maritime passage regimes.
Therefore, treating the Strait of Hormuz as though it were governed solely by innocent-passage rules overlooks the special legal status afforded to international straits under UNCLOS.
The UN Charter and the Use of Force at Sea
While UNCLOS governs navigation, disputes in the Strait often raise broader questions concerning the legality of force.
Article 2(4) of the UN Charter obliges all states to refrain from the threat or use of force against the territorial integrity or political independence of any other state. This fundamental principle applies not only on land but also in the maritime domain, encompassing actions such as attacks on ships, naval blockades, the deployment of sea mines, and other forms of coercive interference with navigation.
Accordingly, if a state were to employ military force to obstruct or prevent the passage of vessels through the Strait, such conduct would likely be regarded as falling within the prohibition established by Article 2(4). Thus, the lawfulness of these measures depends on whether they can be justified under one of the recognized exceptions to the general prohibition on the use of force under international law.
The primary exception to the prohibition on the use of force is contained in Article 51 of the UN Charter, which affirms the inherent right of states to act in individual or collective self-defence when faced with an armed attack. However, the exercise of this right is subject to well-established requirements under international law, particularly the principles of necessity and proportionality. Hence, circumstances such as political disagreements, economic sanctions, diplomatic tensions, or hostile statements, on their own, do not provide a sufficient legal basis for resorting to the use of force.
Consequently, states operating in or around the Strait of Hormuz must demonstrate a clear legal basis before resorting to military measures.
The Oil Platforms Case and Maritime Self-Defence
One of the most important judicial decisions concerning maritime security in the Gulf region is the 2003 judgment of the International Court of Justice (ICJ) in Oil Platforms (Iran v. United States).
Although the dispute formally concerned the interpretation of the 1955 Treaty of Amity between Iran and the United States, the Court's analysis of self-defence has broader significance. The United States argued that its attacks on Iranian oil platforms were justified by self-defence. The ICJ, however, found that the evidence presented was insufficient to support that claim.
The judgment reinforced several important principles. First, states invoking self-defence must establish a sufficient factual basis linking the alleged attack to the state being targeted. Second, defensive measures must be necessary and proportionate. Third, broad claims of strategic necessity or generalized security concerns are unlikely to conform to international legal standards.
The case demonstrates that international courts apply rigorous scrutiny to assertions of self-defence, particularly in maritime contexts where competing narratives and disputed facts are common.
Seizure of Merchant Vessels
The detention of commercial vessels has become one of the most visible manifestations of legal disputes in the Strait of Hormuz. States have justified such actions on various grounds, including alleged navigational violations, collisions, customs infractions, or domestic legal orders.
International law recognizes the authority of coastal states to enforce certain regulations relating to safety, pollution, and customs. Nevertheless, these powers must be exercised consistently with the transit-passage regime.
The legality of a tanker seizure therefore depends on more than the official justification provided. The critical question is whether the action constitutes a genuine and proportionate enforcement measure or whether it is being used as a political instrument to exert pressure on another state.
The 2019 seizure of the Stena Impero illustrates this issue. Numerous legal commentators had regularly argued that the detention appeared retaliatory in nature and was difficult to reconcile with the requirements of transit passage under UNCLOS. If enforcement actions are motivated primarily by geopolitical disputes rather than legitimate regulatory concerns, their compatibility with international law becomes highly questionable.
Can the Strait of Hormuz Be Closed?
A central issue in discussions concerning the Strait of Hormuz is whether Iran possesses the legal authority to close the waterway.
Under the legal framework established by UNCLOS, the prevailing view is that such a closure would not be lawful. Article 44 requires states bordering international straits to refrain from obstructing or suspending transit passage. Given that the Strait of Hormuz is widely recognized as a strait used for international navigation, any attempt to block access would be difficult to reconcile with the legal regime governing transit passage.
Some observers point out that Iran is not a party to UNCLOS and has occasionally adopted positions that differ from those reflected in the Convention. However, many scholars and states consider the fundamental principles governing transit passage, particularly the prohibition on obstruction and suspension, to have become part of customary international law. Hence, these obligations are widely regarded as binding regardless of formal treaty participation.
Moreover, an attempted closure would likely raise issues beyond the law of the seas. If enforced through military means such as mines, missile threats, or naval interdictions, it could also constitute a threat or use of force inconsistent with Article 2(4) of the UN Charter.
Naval Escorts and Freedom of Navigation
In response to security concerns, several states have deployed naval forces to protect commercial shipping in and around the Strait. These operations are generally presented as efforts to ensure freedom of navigation and maintain maritime security.
International law permits naval escorts and defensive maritime patrols aimed at protecting vessels and ensuring the safety of lawful navigation. Such activities are lawful only when conducted in accordance with the UN Charter and the law of the sea. However, freedom of navigation does not authorize coercive military operations unrelated to the protection of transit. Article 39 of UNCLOS further requires vessels exercising transit passage to refrain from any threat or use of force against coastal states. Consequently, military actions exceeding legitimate defensive purposes may additionally raise concerns under international law.
The distinction between protective and coercive naval activity remains critical in assessing the legality of foreign military presence in the Strait.
Maritime Safety and Environmental Obligations
The legal framework governing the Strait extends beyond UNCLOS and the UN Charter. International maritime conventions addressing safety and environmental protection also play a significant role.
UNCLOS requires ships exercising transit passage to comply with generally accepted international rules concerning navigation and pollution control. These include regulations designed to prevent collisions and protect the marine environment. Coastal states frequently invoke safety concerns when regulating maritime traffic. International law recognizes these interests but requires that they be pursued through established international standards rather than through arbitrary or politically motivated restrictions.
Accordingly, navigational safety cannot be used as a pretext for obstructing lawful transit or selectively targeting foreign vessels.
State Responsibility and Dispute Resolution
When a state interferes unlawfully with transit passage or uses force contrary to international law, questions of state responsibility arise.
Under the general principles of international responsibility, a state that commits an internationally wrongful act must cease the conduct and provide appropriate reparation where necessary. These consequences apply whether the violation involves unlawful detention of vessels, interference with navigation, or the improper use of force.
UNCLOS also contains mechanisms for dispute settlement. Although states involved in sensitive security disputes often prefer diplomatic solutions, legal avenues remain available. Flag states may issue protests, seek compensation, request the release of vessels and crews, or pursue proceedings before international tribunals.
The limited use of formal litigation in Hormuz-related disputes reflects political considerations rather than uncertainty about the applicable legal principles.
Conclusion
The Strait of Hormuz represents one of the clearest examples of how international law seeks to balance competing interests in a strategically vital region. The legal framework governing the Strait is primarily derived from UNCLOS and the UN Charter. Together, these instruments establish that the Strait is a waterway used for international navigation, protect the right of transit passage, and restrict the circumstances in which force may be employed.
The law permits coastal states to regulate matters such as navigation safety, environmental protection, and customs enforcement, but these powers are carefully limited. They cannot be used to obstruct passage, retaliate against foreign states, or pursue broader geopolitical objectives. Similarly, user states must exercise navigational rights in a manner consistent with the Charter's restrictions on the use of force.
Recent tanker seizures, military deployments, and threats to close the Strait illustrate the continuing tension between strategic interests and legal obligations. Yet the relevant legal principles remain relatively clear. International law strongly disfavours the closure of international straits, discriminatory interference with shipping, and the use of force outside recognized exceptions.
The principal challenge is not identifying the applicable rules but ensuring compliance with them. Ultimately, the stability of the Strait of Hormuz depends not only on military deterrence and diplomatic engagement but also on continued respect for the legal framework that safeguards one of the world's most important maritime passages.
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