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| Lydia Ehisuoria Ohonsi, Esq. |
ABSTRACT
The Strait of Hormuz, through which approximately one-fifth of the world's oil and liquefied natural gas flows daily, has emerged in 2025–2026 as the most consequential flashpoint in contemporary maritime geopolitics. Against the backdrop of United States airstrikes on Iranian nuclear infrastructure and Iran's parliamentary authorisation to close the Strait, this article critically examines the international legal framework governing the waterway, with a particular focus on the transit passage regime under the 1982 United Nations Convention on the Law of the Sea (UNCLOS). It analyses the legality of a state-imposed closure, the implications for the law of armed conflict at sea, contractual and commercial consequences for the global shipping industry, and the structural deficiencies in enforcement mechanisms that the crisis has laid bare. The article concludes that, although a blanket closure would constitute a serious violation of peremptory international norms, the absence of an effective enforcement architecture renders the legal prohibition largely aspirational in the face of determined military action.
I. INTRODUCTION
At its narrowest point—a mere 21 nautical miles between the Iranian coastline to the north and the Omani and UAE coasts to the south—the Strait of Hormuz is at once a geographical bottleneck and a geopolitical pressure valve. As of mid-2025, nearly 20 million barrels of crude oil and approximately one-fifth of the world's liquefied natural gas (LNG) pass daily through this slender maritime corridor, cementing its role as an artery without which energy-dependent economies across Asia, Europe, and beyond could not easily function.
The Strait has once again surged to the forefront of international legal discourse following a confluence of events: United States airstrikes on Iranian nuclear infrastructure, Iran's parliamentary motion authorising the closure of the Strait as a retaliatory measure, and the subsequent escalation of attacks against neutral merchant vessels in the wider Gulf region. These developments collectively raise the most profound questions in modern international maritime law: Can a coastal state lawfully close an international strait? What legal recourse exists for affected shipping interests? And what do these developments reveal about the structural resilience or fragility of the UNCLOS framework?
This article addresses these questions in turn. Part II sets out the legal status of the Strait under UNCLOS and the transit passage regime. Part III analyses the legality of closure under the law of the sea and the law of armed conflict. Part IV examines the commercial and contractual consequences for charterparties and cargo interests. Part V considers enforcement mechanisms and their limitations. Part VI offers a conclusion and reform perspective.
The stakes could scarcely be higher. The simultaneous disruption of the Strait of Hormuz and, since 2023, the Bab el-Mandeb strait at the southern end of the Red Sea has confronted the international shipping industry and, by extension, the global economy with a dual chokepoint crisis unprecedented in its scope and duration since the tanker wars of the 1980s. The legal questions that arise are not merely academic; they will determine the rights and liabilities of thousands of shipowners, charterers, cargo interests, insurers, and financiers whose commercial relationships are governed by contracts whose terms were drafted without anticipation of a conflict of this character. More fundamentally, they test whether the framework of international maritime law, painstakingly constructed over the decades since the Corfu Channel judgment and codified in UNCLOS, is capable of providing effective governance over one of the world's most strategically vital sea lanes.
II. THE LEGAL STATUS OF THE STRAIT OF HORMUZ UNDER UNCLOS
A. Classification as an International Strait
The legal regime applicable to the Strait of Hormuz flows from its classification as an international strait within the meaning of Article 37 of UNCLOS. Article 37 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 connects the exclusive economic zones (EEZs) of the Persian Gulf states to the EEZs of the Arabian Sea littoral states, satisfying this criterion unambiguously. There is no reasonable dispute that the Strait qualifies as an international strait for the purposes of the UNCLOS framework; its character as a global commercial thoroughfare makes this classification inevitable under any defensible interpretation of the Convention.
That the Strait falls within the territorial sea of Iran and Oman—the two bordering states—does not diminish its international legal character. As the International Court of Justice held as far back as 1949 in the landmark Corfu Channel Case, coastal states may not close international straits to the innocent passage of foreign vessels in peacetime; this principle has since crystallised into the more expansive transit passage regime codified under Part III of UNCLOS. The evolution from the Corfu Channel principle of innocent passage to the UNCLOS transit passage regime represents a progressive strengthening of user-state rights: whereas innocent passage could, in some circumstances, be suspended by the coastal state for specified reasons, transit passage under UNCLOS may not be suspended under any circumstances and confers rights on warships and military aircraft that do not exist under the innocent passage regime.
The Traffic Separation Scheme (TSS) recognised by the International Maritime Organization (IMO) divides the Strait into two two-mile-wide shipping lanes—one for inbound and one for outbound traffic—traversing Iranian and Omani territorial waters respectively. There is no alternative deep-water sea route for the Persian Gulf littoral states. Several states, including Kuwait, Qatar, Bahrain, and Israel, possess no viable bypass for their maritime trade. This geographical reality lends additional legal force to the proposition that the Strait is indispensable to global commerce and is, therefore, subject to the most stringent navigational protections international law can provide.
B. The Transit Passage Regime: Rights and Duties
The cornerstone of the applicable legal framework is the right of transit passage under Articles 37 to 44 of UNCLOS. Transit passage is defined in Article 38(2) as the exercise of freedoms of navigation and overflight solely for the purpose of continuous and expeditious transit. It is a more robust right than innocent passage: it cannot be suspended under any circumstances, applies to all ships and aircraft—including warships and military aircraft—and does not require prior notification to, or authorisation from, the coastal state. This last feature distinguishes the transit passage regime sharply from the innocent passage regime applicable to the territorial sea generally, and reflects the particular importance accorded by the drafters of UNCLOS to the maintenance of freedom of navigation through strategically critical straits.
The obligations on user states are concomitant. Ships and aircraft in transit must proceed without delay, refrain from any threat or use of force against the sovereignty, territorial integrity, or political independence of states bordering the strait, and comply with generally accepted international regulations concerning safety at sea. Submarines and other underwater vehicles must navigate on the surface and show their flag—a requirement that distinguishes transit passage from the high-seas freedom of navigation, under which submarines may proceed submerged.
The duties on strait states are equally clear. Article 44 provides that strait states "shall not hamper transit passage" and shall give appropriate publicity to any danger to navigation or overflight in the strait within their knowledge. Critically, strait states are prohibited from suspending transit passage. Their regulatory competence is limited to adopting laws regarding safety of navigation, prevention of pollution, customs, fiscal, immigration, and sanitary matters—but such laws may not have the practical effect of denying, hampering, or impairing the right of transit passage. The asymmetry between the breadth of user-state rights and the narrowness of coastal-state regulatory authority is one of the most significant features of the transit passage regime and remains a source of persistent tension with Iran's own claims of navigational authority over the Strait.
It bears emphasising that Iran is not a party to UNCLOS. Neither are the United States nor Israel. However, the transit passage provisions of UNCLOS are widely regarded as reflecting customary international law, binding on all states regardless of treaty ratification. Iran has, on previous occasions, acknowledged international navigational freedoms in the Strait even while asserting particular sovereign claims, suggesting a degree of implicit acceptance of the customary norm. The argument that a non-party to UNCLOS cannot be bound by its transit passage provisions is legally unpersuasive given the overwhelming state practice and opinio juris supporting the customary status of those provisions.
III. LEGALITY OF CLOSURE UNDER INTERNATIONAL LAW
A. Closure in Peacetime: A Clear Violation
There can be little legal controversy regarding a peacetime closure of the Strait of Hormuz. Such a closure would directly violate Articles 38 and 44 of UNCLOS, the customary international law principle established in the Corfu Channel Case, and the general prohibition on hampering freedom of navigation. The prohibition is unambiguous in its terms, and the absence of exception clauses in the relevant UNCLOS provisions leaves no textual room for a lawful peacetime suspension.
Iran's domestic legal arguments have invoked the concept of national security to justify restricting navigational rights. This argument is legally untenable. Transit passage is a lex specialis regime under UNCLOS that cannot be suspended even in response to acts characterised as aggression. The relevant provisions impose an absolute prohibition without exception clauses for national security or reprisals. The drafting history of UNCLOS confirms that the prohibition on suspension was a deliberate and contested choice, negotiated with full awareness that strait states might wish to preserve the ability to restrict passage in exceptional circumstances; the rejection of such exceptions is thus absolute and cannot be circumvented by analogy with other areas of international law.
Moreover, the invocation of countermeasures as a justification fails under the International Law Commission (ILC) Articles on State Responsibility. Countermeasures cannot derogate from peremptory norms (jus cogens) or from obligations under the UN Charter. The freedom of navigation through international straits is sufficiently fundamental that any forcible interference—particularly one with foreseeable catastrophic consequences for third-state economies—cannot be reduced to a permissible countermeasure under customary international law.
B. Closure in Times of Armed Conflict: The Law of Armed Conflict at Sea
The legality analysis becomes considerably more complex in the context of active armed hostilities. The foundational principle, derived from the Corfu Channel judgment and affirmed by the San Remo Manual on International Law Applicable to Armed Conflicts at Sea, is that states are required to ensure safe passage through international straits to neutral ships and aircraft.
A belligerent state—even one whose territorial waters encompass the Strait—is not entitled to close an international strait to neutral shipping by laying minefields, imposing naval blockades, or through direct interdiction. Rule 102 of the San Remo Manual confirms that a blockade may not bar access to neutral ports or the passage of neutral vessels through international straits.
The minelaying prohibition deserves particular attention in the current context. The 1907 Hague Convention (VIII) requires that automatic submarine contact mines must be anchored and rendered harmless once cut from their moorings. The use of mines in a manner that indiscriminately threatens neutral commercial navigation violates both the Hague Conventions and the customary rules of proportionality and discrimination under the law of armed conflict.
Reports emerged in early 2026 that Iran may be mining the Strait—an act that would constitute a significant escalation under international law. If confirmed, such mining activity would not only violate the navigational rights of neutral commercial shipping but would also engage Iran's international responsibility for any resulting casualties and property damage, and could constitute a triggering event for collective self-defence responses by affected states and their allies.
Attacks against neutral merchant vessels raise acute issues of targeting under the law of naval warfare. Neutral merchant vessels enjoy protected status under the San Remo Manual unless they make an effective contribution to an enemy's war effort, and they cannot be legitimately targeted absent reasonable warning and compliance with visit-and-search procedures. Summary attacks without such process are unlawful.
C. The "Lawfare" Dimension: Strategic Legal Ambiguity
Scholars have observed that Iran has pursued a strategy of "lawfare"—the deliberate exploitation of legal ambiguity to contest transit rights and generate uncertainty that deters commercial passage even without a formal closure. This has involved a range of instruments: the use of Iran's Traffic Separation Scheme enforcement authority to arrest foreign tankers (as with the Stena Impero in 2019 and the MSC Aries in 2024), GPS and AIS jamming and spoofing operations that create hazards to safe navigation, and threatening VHF broadcasts purporting to declare the Strait closed.
The UKMTO explicitly addressed this in its March 2026 advisory, clarifying that VHF broadcasts declaring the Strait "shut down" are not legally binding and do not constitute lawful restrictions on navigation under international law. The lawfare strategy is thus legally ineffective but commercially devastating: it achieves its aims not by the force of law but by the force of fear, and the distinction between the two is of limited practical comfort to a master navigating the Strait under the implicit threat of naval interdiction.
IV. COMMERCIAL AND CONTRACTUAL CONSEQUENCES FOR THE SHIPPING INDUSTRY
A. Charterparty Implications: War Risk Clauses
The closure or effective blockade of the Strait of Hormuz generates immediate and far-reaching consequences for the contractual framework of international shipping. The primary vehicle through which these consequences are managed is the war risk clause incorporated into charterparties. The BIMCO CONWARTIME and VOYWAR clauses, substantially updated in 2025, are the most widely used instruments in this regard.
Under the revised CONWARTIME 2025, owners are entitled to refuse employment orders requiring a vessel to proceed to or remain in an area where, in the Master's reasonable judgment, the vessel may be exposed to war risks. This right applies regardless of whether the risk existed when the charterparty was concluded or arose only thereafter. The 2025 formulation introduces an important innovation: owners must now demonstrate that they have used "reasonable endeavours" to obtain competitive insurance terms before claiming additional premiums from charterers, giving charterers scope to challenge excessive or opportunistic premium claims.
The practical consequence is significant. Where BIMCO War Risk Clauses are incorporated, owners who decline orders directing their vessels into the Strait will likely be contractually justified in their refusal, given the documented escalation of military activity and the JMIC's upgrading of its regional risk assessment to "critical"—indicating that attacks are assessed as almost certain absent significant de-escalation. However, owners must exercise caution: a refusal to proceed must be genuinely founded in a reasonable assessment of risk rather than commercial opportunism, and an unreasonable deviation may deprive the carrier of contractual defences, impair bill of lading rights, and potentially jeopardise insurance cover.
B. Force Majeure and Frustration
For carriers who do not have war risk clauses, or whose clauses are drafted narrowly, the alternative legal pathways are force majeure and frustration. However, both doctrines present significant hurdles. Force majeure is a civil law concept that does not form part of English common law except to the extent incorporated expressly into a contract. In common-law jurisdictions, particularly England—whose law governs the majority of international charterparties—the relevant doctrine is frustration. A party claiming frustration must demonstrate that the changed circumstances have fundamentally altered the obligation as compared to what was undertaken by the contract, and that the change was not foreseeable at the time of contracting.
Given that tensions in the Hormuz region have been a recurring feature of the geopolitical landscape for decades—encompassing the tanker wars of the 1980s, the Stena Impero seizure of 2019, and multiple Iranian threats of closure in intervening years—courts may be reluctant to find genuine frustration in circumstances that experienced maritime operators arguably should have anticipated and provided for contractually. The legal principle that frustration is not available where the supervening event was foreseeable is well established in English law and is likely to pose a significant barrier to frustration claims arising from the current crisis.
The position differs across civil-law jurisdictions. European carriers operating under French, Dutch, or German law will generally find force majeure easier to invoke given the broader and more flexible treatment of the doctrine in those legal systems, which do not require the supervening event to be wholly unforeseeable but merely that it render performance impossible or unreasonably burdensome. This divergence creates the prospect of inconsistent outcomes across jurisdictions for what are, in commercial terms, substantially identical situations—a significant source of legal uncertainty for international traders and their financial counterparties.
C. Insurance Implications
The insurance market has responded swiftly and dramatically to developments in the Strait. War risk premiums for Hormuz transits increased by an estimated 400–600% between January and March 2026, with a significant number of underwriters declining to offer cover at any premium. Blocking and trapping insurance—which covers instances where a vessel is prevented from leaving a port or area due to obstruction, blockade, or military detention—has come sharply into focus for vessels engaged in Persian Gulf trade.
The practical effect of insurance market withdrawal compounds the legal uncertainty for shipowners. Even where a vessel has a contractual right to transit, the absence of viable insurance cover may render the exercise of that right economically impossible. International law may declare the Strait open; the insurance market effectively closes it.
D. Deviation, Rerouting, and Alternative Routes
The principal alternative to Hormuz transit is rerouting around the Cape of Good Hope—a deviation that adds approximately 3,500 to 4,000 nuclear miles and twelve to fifteen additional sailing days for vessels bound for European ports, with commensurate increases in fuel costs, time charter hire exposure, and laytime implications. Where Suez Canal transits are also disrupted by Houthi activity in the Red Sea—as has been the case since 2023–2024—the diversion challenge becomes still more acute, with some analysts characterising the simultaneous disruption of Hormuz and Bab el-Mandeb as an effective maritime siege of a substantial portion of global energy and container trade.
VI. ENFORCEMENT MECHANISMS AND THEIR STRUCTURAL LIMITATIONS
A. UNCLOS and Its Dispute Resolution Architecture
The absence of effective enforcement mechanisms is the structural Achilles heel of the international maritime law framework as applied to the Strait of Hormuz. UNCLOS provides for compulsory dispute resolution through ITLOS, the ICJ, or arbitral tribunals under Annex VII. However, Article 298(1)(b) permits states to exclude from compulsory settlement "disputes concerning military activities, including military activities by government vessels and aircraft engaged in non-commercial service." This exclusion is broad enough to encompass virtually all of the conduct currently at issue in the Hormuz crisis. Moreover, neither Iran, the United States, nor Israel are parties to UNCLOS, significantly limiting the formal treaty-based avenues for legal redress.
B. The UN Security Council: Paralysis and Limited Precedent
The UN Security Council is the principal body with authority to impose binding measures in response to threats to international peace and security under Chapter VII of the UN Charter. The historical precedent of Security Council Resolution 598 (1987), adopted during the Iran–Iraq Tanker War, provides some guidance: the Council was able to call for a ceasefire and freedom of navigation, though enforcement was patchy and ultimately dependent on US naval escort operations. Operation Earnest Will—in which Kuwaiti tankers were re-flagged under the US flag and escorted through the Gulf by naval warships—demonstrated that unilateral naval power, rather than multilateral legal authority, was ultimately decisive in maintaining the flow of commerce through the Strait.
In the current political environment, Security Council action is effectively foreclosed by the likelihood of a veto. The permanent membership of the Council, fractured by competing alignments in the Iran–US–Israel triangle, renders collective binding action improbable. The Council's residual role is therefore primarily one of legitimation—providing a forum within which legal obligations may be publicly articulated and political pressure applied—rather than one of enforcement. The irony is stark: the institution whose authority is most needed to give effect to the navigational rights guaranteed by international law is the institution least capable of delivering that effect.
C. Structural Gaps in the Legal Framework
Analysis of the Hormuz crisis identifies at least three structural gaps in the international legal system. First, there is the inadequacy of attribution thresholds in addressing state-sponsored proxy maritime violence: the ILC's framework of effective control, as interpreted by the ICJ, has difficulty capturing the role of the IRGC and its affiliated non-state proxies in attacks on commercial shipping in a manner that clearly engages Iranian state responsibility without additional evidence of direct instruction. Second, there is the absence of interim enforcement mechanisms capable of responding to transit passage violations at a speed commensurate with the maritime context: international litigation moves on timescales of years, while commercial shipping must make routing decisions in hours. Third, there is the failure to develop regional governance frameworks for critical chokepoints that incorporate both coastal and user-state perspectives in a binding and operationally effective manner.
These gaps are not unique to Hormuz. The enforcement fragmentation that characterises contemporary maritime law—in which flag-state jurisdiction, port-state control, and international supervisory mechanisms operate in silos with limited coordination and significant political interference—renders international maritime law structurally incapable of responding effectively to determined state or quasi-state actors willing to absorb the reputational costs of norm violation. The Hormuz crisis is thus not an aberration but a culmination: it exposes, in the most acute and damaging terms, the foundational tension in international maritime law between its aspirations to universal governance and its dependence on voluntary compliance for its effectiveness.
VI. CONCLUSION AND REFORM PERSPECTIVE
The ongoing crisis in the Strait of Hormuz is a stress test of the UNCLOS framework—and the framework, if not formally failing, is showing severe strain. The legal prohibition on closing international straits is unambiguous: Articles 38 and 44 of UNCLOS, customary international law, and the Corfu Channel principle combine to render any forcible denial of transit passage to neutral commercial vessels a violation of international law. In the context of active armed hostilities, the San Remo Manual and the general law of armed conflict reinforce this conclusion, particularly in relation to attacks on neutral shipping and the indiscriminate use of naval mines.
The legal analysis, viewed in isolation from political realities, is thus relatively clear: Iran has no lawful basis in international law for closing the Strait, and individual attacks on neutral merchant vessels are straightforwardly unlawful. Yet the normative clarity of the prohibition stands in sharp contrast to the practical impotence of its enforcement. The combination of non-party status (Iran, USA, Israel), compulsory settlement exclusions for military activities, Security Council paralysis, and the structural inadequacy of existing enforcement mechanisms means that the legal prohibition functions largely as an aspiration rather than a guarantee. Commercial actors—shipowners, charterers, cargo interests, and insurers—must therefore navigate this crisis through the lens of contract, commercial prudence, and insurance architecture rather than the confident application of international legal rights.
Several reform trajectories deserve serious consideration. First, the international community should develop mandatory compulsory settlement mechanisms for transit passage disputes that cannot be excluded by Article 298 reservations, given the systemic economic consequences of chokepoint disruption. The existing architecture permits states to opt out of adjudication at precisely the moment when adjudication is most needed; reform should seek to make jurisdiction over transit passage violations mandatory and automatic, at least where the disruption causes demonstrable harm to third-state commerce.
Second, regional governance frameworks for strategically critical straits should be developed, incorporating user-state participation and binding safety obligations on coastal states. The Montreux Convention regime for the Turkish Straits provides a partial model, having demonstrated over nearly ninety years that a treaty regime specifically tailored to the character of a particular strait can provide a more stable and enforceable framework than UNCLOS's general provisions. An analogous regime for the Strait of Hormuz—one that acknowledges Iran's legitimate security interests while guaranteeing navigational freedoms for neutral commercial shipping—would require diplomatic investment of considerable depth and duration, but represents the most structurally sound long-term solution.
Third, the IMO should be empowered with enhanced monitoring and operational response capabilities in critical chokepoint areas, moving beyond its current purely advisory and regulatory mandate. Enhanced IMO capacity—including the ability to deploy maritime safety coordinators, maintain real-time traffic monitoring, and coordinate with naval presences in disputed areas—would at a minimum improve the information environment available to commercial operators and provide a basis for more rapid international responses to violations.
The Strait of Hormuz crisis is, at its core, a crisis of the international legal order's capacity to maintain the conditions for global economic interdependence against the determined assertion of sovereign power. The legal principles are clear; the enforcement architecture is not. Closing that gap is among the most urgent and challenging tasks of international maritime law in the decades ahead. The lessons of the Hormuz crisis—like those of the tanker wars before it, and the dark fleet crisis alongside it—point inexorably to the same conclusion: international maritime law requires not merely clearer rules, but the institutional machinery and political will to make those rules effective in the real world of states, power, and commercial interest.
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