Mainstream WeeklyBarely a month after reopening the Strait of Hormuz under the Memorandum of Understanding (MoU) signed on June 17 to end the war, Iran has declared the waterway closed again “until further notice”—signalling the collapse of a deal many had regarded from the outset as inherently fragile. The resumption of hostility is a stark reminder of an enduring truth: it is far easier to start a war than to end one. Interestingly, the renewed confrontation is no longer centred on Iran’s nuclear programme or missile capabilities - the original casus belli—but on competing claims to regulate one of the world’s most strategic maritime chokepoints.
The latest escalation began on July 7 when Iranian forces attacked three commercial vessels—a Qatar-owned liquefied natural gas (LNG) tanker, a Saudi-owned crude oil tanker and a Liberia-flagged crude carrier—as they attempted to transit the Strait of Hormuz, allegedly in defiance of repeated warnings. Earlier in May, Tehran had established the Persian Gulf Strait Authority (PGSA) to regulate navigation through the Strait and required all commercial vessels to follow shipping routes designated by the Authority, warning that any departure from those routes would invite a "forceful response". The vessels were reportedly using a U.S.-recommended route through the southern channel in Oman’s territorial waters, in defiance of Iran’s routing directives.
Presenting the Iranian attacks as an unacceptable threat to freedom of navigation, Washington responded with a swift and expansive military campaign. Within hours, it launched retaliatory airstrikes that continue unabated against dozens of military and strategic positions allegedly used to target commercial vessels transiting the Strait, including coastal surveillance installations and air defence facilities. Simultaneously, it revoked temporary sanctions waivers and reimposed the naval blockade on Iranian oil exports that had been lifted only weeks earlier under the June MoU.
The speed and scale of the U.S. response suggest that the Iranian attacks have given the Trump administration the opportunity it may have been waiting for to resume military strikes against Iran. President Trump promptly declared that the ceasefire was "over". This was followed on July 18 by Iran’s announcement that it was suspending the implementation of all its obligations under the MoU, accusing Washington of systematically violating the agreement over the preceding week, leaving little doubt that the peace framework had effectively collapsed. Together, these developments have once again brought an already volatile region to the brink of a full-scale war.
At the heart of the renewed confrontation lie competing U.S. and Iranian claims over transit passage through the Strait of Hormuz, which, ironically, was never a point of contention when hostilities began at the end of February. Before the outbreak of war, the Strait remained open to uninterrupted international shipping, facilitating the daily transit of nearly one-fifth of the world’s traded oil and liquefied natural gas exports from the Persian Gulf.
Having effectively closed the Strait of Hormuz in response to the U.S.-Israeli attacks in February, sending shockwaves through global energy markets, Tehran now appears determined to preserve its ability to regulate access to the waterway as a source of strategic deterrence and diplomatic leverage. Viewing effective control over the Strait as vital to its national security, it insists that commercial vessels transit only through designated shipping lanes in Iranian waters near Larak Island and comply with its navigational directives. Iran further maintains that it is entitled to regulate passage through the Strait and has repeatedly declared that there will be no return to the pre-war regime of unrestricted navigation. Tehran is also seeking international recognition of its claimed right to levy transit fees on commercial shipping and has reportedly enforced its routing directives by using force against vessels that fail to comply.
The United States, for its part, maintains that the Strait of Hormuz is an international waterway and cannot be subject to the kind of unilateral regulation asserted by Iran. It insists that commercial vessels must enjoy uninterrupted freedom of navigation and has encouraged shipping to transit through the southern channel in Oman’s territorial waters under the protection of the U.S.-led naval presence, thereby seeking to undermine Iran’s bid to control the Strait. Reinforcing this position, U.S. Secretary of State Marco Rubio recently accused Tehran of attempting to use the strategic waterway as a bargaining tool, arguing that such conduct undermines the principle of free navigation through international straits. Washington has consequently sought to frustrate every Iranian attempt to transform the Strait into an instrument of political or strategic coercion.
The United States has sought to justify its military action against Iran in the name of safeguarding freedom of navigation and the uninterrupted flow of global commerce. Yet Trump’s proposal to impose a 20 per cent security fee on commercial shipping for the protection provided by what he described as the "Guardian of the Hormuz Strait"—though eventually withdrawn following widespread international criticism— revealed the tension between Washington’s legal rhetoric and the underlying intent behind the proposal. The driving force behind Washington’s invocation of freedom of navigation, therefore, may not be altruism or the common good alone, but the pursuit of its own strategic and economic interests in maintaining control over one of the world’s most vital maritime chokepoints.
Ironically, rather than resolving the legal controversy over the Strait of Hormuz, the ambiguous formulation of the MoU appears to have reinforced Iran’s long-standing claim that it retained a residual authority to regulate navigation through the Strait after the expiry of the sixty-day commitment. Article 5 requires Iran to make its "best efforts" to ensure the safe passage of commercial vessels without levying any charges, but only for a period of sixty days. Recognising the practical need to remove military obstacles and undertake demining operations, the MoU also granted Tehran a thirty-day transition period. More significantly, while the provision guarantees the passage of commercial shipping, it is conspicuously silent on the status of warships, government vessels and military aircraft.
The ambiguity becomes even more pronounced with reference to the future "management and maritime services" of the Strait, to be worked out through consultations among Iran, Oman and the Gulf States. Although the MoU requires that any future arrangements conform to applicable international law and the sovereign rights of coastal States, it excludes the United States from those consultations. The provision therefore leaves considerable room for competing interpretations of the parties’ rights and obligations. Tehran may consequently contend that, following consultations with Oman and the other Gulf littoral States, it is entitled to prescribe navigational rules governing transit through the Strait, including designated shipping routes, prior notification requirements and even transit charges.
The “applicable international law” to which the MoU requires any future arrangements for the management of the Strait of Hormuz to conform is itself far from settled. Although the Strait falls within the territorial seas of Iran and Oman, it is generally regarded under UNCLOS as a strait used for international navigation to which the regime of transit passage applies. This regime affords ships and aircraft a broader freedom of navigation than the ordinary right of innocent passage through the territorial sea.
Iran has never ratified UNCLOS and is therefore not bound by the Convention as a matter of treaty law, except insofar as particular provisions reflect customary international law. Moreover, when signing the Convention, Iran issued an interpretative declaration rejecting the applicability of its provisions on transit passage. Even if aspects of UNCLOS, particularly the regime of transit passage, are regarded as reflecting customary international law, Tehran could still seek to invoke the persistent objector doctrine to argue that those rules are not opposable to it. Iran has consistently maintained that the Strait of Hormuz is instead governed by the regime of innocent passage, which affords coastal States greater regulatory authority within their territorial seas.
Even the regime of transit passage, however, does not strip coastal States of all regulatory authority. Although UNCLOS prohibits the imposition of charges merely for the exercise of transit passage, it recognises the right of States bordering straits to regulate navigation in limited circumstances, including by designating sea lanes and establishing traffic-separation schemes, as well as adopting laws relating to navigational safety and the regulation of maritime traffic. Consistent with this principle, the existing routing arrangements in the Strait of Hormuz were developed jointly by Iran and Oman in 1968. The central legal question, therefore, is not whether Iran possesses any regulatory authority over navigation through the Strait, but whether the measures it seeks to impose fall within the limited regulatory powers recognised by international law or effectively impair the right of transit passage itself.
That question becomes more complex in the context of armed conflict. The challenge is not merely to determine the limits of the regulatory authority of States bordering strait, but also to reconcile their legitimate security concerns with the international community’s interest in preserving uninterrupted maritime navigation. Historical State practice recognised significant belligerent authority to interfere with navigation through international straits, including the denial of passage to enemy vessels and aircraft, while the position regarding neutral shipping remained more contested. Even after the emergence of the modern regime of transit passage, State practice has continued to reveal a tension between the principle of uninterrupted navigation and the security imperatives of belligerent littoral States, which have at times sought to restrict or even close international straits during wartime.
The Strait of Hormuz exposes this tension with particular force. A legal regime that protects international navigation while treating the security concerns of the States whose territorial seas constitute an international strait as merely an exception risks becoming detached from the realities of armed conflict. Yet the answer cannot lie in allowing a coastal State to convert security into a pretext for unilateral control, closure or taxation. The challenge is to accommodate genuine security measures without allowing them to become a vehicle for the permanent erosion of international navigation rights. The future of the Strait may therefore depend not on choosing between freedom of navigation and coastal-State security, but on developing a legal framework capable of protecting both.
(Author: Aftab Alam is Professor and Dean, Faculty of International Studies, Aligarh Muslim University, India)