UNCLOS Under Pressure
- Greta Fedeli
- 2 days ago
- 12 min read
Between law and power: governance challenges in maritime chokepoints
The recent crisis involving the Strait of Hormuz has demonstrated the fragility of international commerce. Approximately 85% of global trade volume moves by sea; however, most of this traffic flows through a limited number of critical maritime chokepoints, including the Strait of Hormuz, the Strait of Malacca, and the Turkish Straits. The systemic vulnerability of these narrow waterways and the lack of practical alternatives allow States to leverage geography for strategic advantage, making it possible even for relatively weak powers to disrupt the global supply chain.
In this context, realpolitik intersects uneasily with international law. Under the UN Convention on the Law of the Sea (UNCLOS), straits used for international navigation are subjected to a particular legal regime which strives to balance freedom of navigation with the rights and interests of coastal States. First through the innocent passage regime and then through the transit passage regime, UNCLOS aims to ensure unimpeded transit and neutrality of maritime routes without undermining States’ territorial sovereignty.
Yet, when it comes to a competitive multipolar global order of interconnected economies, the increasing significance of maritime chokepoints in terms of politics, commerce, and strategy has turned them into critical tools of coercion and power projection. While UNCLOS remains the foundational legal framework of the law of the sea, its de facto effectiveness is limited by the weaponization of critical chokepoints by State actors. As a result, the regulation of straits is governed by a complex interplay between geopolitical realities defined by asymmetric network structures and international law.
Maritime Chokepoints: the bottlenecks of maritime trade
Maritime chokepoints are critical narrow sea passageways that connect larger bodies of water and facilitate transit of substantial trade volumes. Due to their pivotal role in connecting major regions worldwide, they are often defined as “international maritime highways”. However, as shipping routes are concentrated in a limited number of critical junctures, these chokepoints are considered bottlenecks for maritime transport: any disruption can create a ripple effect across supply chains, leading to supply delays and increasing shipping prices.
On the global stage, the main maritime chokepoints are the Strait of Hormuz, the Panama Canal, the Strait of Malacca, the Suez Canal, and the Strait of Bab el-Mandeb.
The Strait of Malacca, connecting the Indian Ocean to the Pacific Ocean, and the Strait of Hormuz, linking the Persian Gulf and the Gulf of Oman, are the world’s most important strategic chokepoints by volume of oil moved, accounting respectively for 29% and 20% of total global maritime traded oil. Of the crude oil and condensate transiting through the Strait of Hormuz, approximately 89% is destined to Asian markets.
Moreover, the Suez Canal, a 193-kilometer canal connecting the Red Sea and the Mediterranean Sea, is the fastest route between Asia and Europe and it alone handles 12% to 15% of global trade and 30% of global container traffic.
While under normal conditions these chokepoints increase the efficiency of global trade by reducing the time and cost of transportation, their strategic importance and the lack of expedient alternatives make them structurally vulnerable to geopolitical tensions, piracy, and terrorism. As a result, the global economy depends directly on the continuity of transit through these critical sea routes.
The Legal Framework: the UN Convention on the Law of the Sea (1982)
Modern law of the sea derives mostly from the 1982 UN Convention on the Law of the Sea (in force from 1994), which followed the four 1958 Geneva Conventions on the Law of the Sea and may be considered a reflection of international customary law. This legal framework is rooted in the vision of Dutch jurist and philosopher Hugo Grotius outlined in his work Mare Liberum (1609), in which he set forth the principle of freedom of navigation, claiming that the sea is international territory and, as such, open to all nations for trade and navigation.
The special status of international straits was first clearly acknowledged in the Corfu Channel case (1949), where the International Court of Justice (ICJ) recognized the existence of a distinctive international customary right of innocent passage through straits used for international navigation. The Court claimed that, unless differently prescribed by a convention, coastal States could not prohibit innocent passage of warships and merchant ships through a strait in peacetime. It also provided a legal definition of the straits subject to this regime, identifying as decisive criteria its geographical situation as connecting two parts of high seas and the fact of it being used for international navigation, thus rendering irrelevant the volume of traffic passing through the strait, its importance, or the presence of alternative routes.
While the Corfu Channel case remains a pillar of the law of the sea, the innocent passage regime proved to be inadequate in guaranteeing freedom of navigation within international straits, especially when considering that it was allowed for a coastal State to temporarily suspend innocent passage under certain conditions. To overcome the issue, the UN Convention on the Law of the Sea introduced the more extensive transit passage regime, while granting littoral States some regulatory powers.
Under UNCLOS, navigation is governed by two different regimes: innocent passage and transit passage. The former continues to apply within the territorial sea, while the latter applies to straits used for international navigation in accordance with the provisions of Part III of the Convention. Specifically, transit passage is enjoyed by ships when transiting through straits used for international navigation between one part of the high seas and the exclusive economic zone (EEZ), and another part of the high seas or EEZ. The most important distinction between the two regimes is that, unlike innocent passage, transit passage cannot be suspended by coastal States: even if a strait State is concerned about its national security, it remains under an obligation to continue to permit transit.
The legal efficacy of UNCLOS: the interplay between law and geopolitics
The transit passage regime has exposed many areas where UNCLOS remains silent, highlighting how maritime chokepoints are subject to many geopolitical and security threats. The Convention tries to balance freedom of navigation rights with the rights of coastal States, relying on a deliberately broad language which may, in some instances, appear ambiguous. This uncertainty allows for different interpretations to be strategically exploited by States.
Despite the clear geographical and functional criteria adopted to define the scope of application of Part III, the identification of those international straits within which the right of transit passage applies and those waterways properly characterized as straits within which alternative UNCLOS regimes apply remains a critical operational issue. For example, transit passage applies if the strait is overlapped by the territorial sea of the bordering States; however, littoral States, through the laws and regulations they are allowed to enact in relation to transit passage, may adopt particular positions on the transit regime when it applies within the territorial sea of that State.
The legal efficacy of UNCLOS depends on States’ cooperation and their commitment to uphold the law. In the absence of a centralized enforcement mechanism, compliance is left to the individual actors. As a result, national interests are often prioritized over legal obligations and power dynamics between States become a primary factor shaping the governance of international straits.
The greater the strategic importance of the strait, the more difficult it is for the law to be effective. The main issue with UNCLOS Part III, when it comes to maritime chokepoints, is that its assumptions of neutrality of maritime corridors and freedom of navigation no longer hold within global trade networks characterized by asymmetric interdependence.
States weaponize interdependence by leveraging control over straits, increasingly relying on grey zone measures to pursue their strategic objectives. These tactics involve coercive actions that remain below the threshold of armed conflict, falling in the area between peace and war: they include indirect or undeclared limits on maritime transit imposed through legal, economic, or regulatory mechanisms, the use of non-State actors to disrupt maritime stability and security, and other non-traditional methods. While they may vary in practice, all these measures have a common denominator: they allow States to exercise coercive pressure without overtly violating international law or resorting to open warfare.
The governance challenges posed by navigation within international straits emerge clearly in the Strait of Hormuz, a vital oil maritime chokepoint linking the Persian Gulf with the Gulf of Oman and the Arabian Sea. While the majority of the shipping lanes are located in the territorial waters of Oman and partially in the Iranian territorial waters, this waterway legally qualifies as a strait used for international navigation, thus it is governed by Part III of UNCLOS.
Despite being subject to the transit regime, Iran dominates the strait thanks to its proximity and has exercised extensive control over it. While already subject to controversies in the past, since the start of the Iran-US conflict the strait has become a key element of a crisis that has affected the entire global energy market.
During the first stages of the conflict, Iran effectively obstructed navigation through the strait. While avoiding declaring a full closure, the country adopted a selective policy under which it allowed the transit of vessels from States considered friendly or neutral, requiring coordination with Iranian authorities and the payment of a toll, while prohibiting the passage of vessels associated with countries deemed as enemies. Moreover, Iran employed other strategies, such as the deployment of naval mines, to further delay and deter passage through the strait.
From a legal point of view, under the transit regime, unimpeded passage is guaranteed through international straits, even during war times; therefore, coastal states, Iran included, are not allowed to disrupt navigation. Iran argues that it is not bound by UNCLOS because, despite being a signatory party to the convention, it has not ratified it; instead, the country claims that within its territorial waters the more restrictive regime of innocent passage applies due to its persistent objection to recognize transit passage as an international custom.
This argument is usually deemed as unpersuasive and is limited by the widely and generally accepted view that the right of transit passage is a principle of international customary law, thus binding on all countries, even non-parties.
The response from the US has been a military blockade of Iranian ports, both inside and outside the strait of Hormuz, although, according to US representatives, not of the strait itself. On one hand, while the US has neither signed nor ratified UNCLOS, it accepts it as representative of international customs and is therefore bound to comply with the transit regime and to refrain from infringing the right of freedom of navigation within the strait. On the other hand, a blockade is a wartime measure that denies access or departure from specific maritime areas and is governed by a different legal regime, the law of armed conflict at sea.
This still evolving situation illustrates how the efficacy of the legal framework governing international straits does not rely solely on formal rules, but also on the underlying dynamics between States and their willingness to comply with their legal obligations under international law.
Economic and Legal Implications
The governance issues over international straits raised by the Hormuz crisis have broader implications when considering the role of maritime chokepoints in global trade and the framework outlined by UNCLOS. In this context, two central elements emerge: on one hand, what lies at the heart of these maritime bottlenecks is a trade-off between efficiency and security; on the other hand, the increasing centrality of maritime chokepoints in international trade is reshaping how States interpret and consider freedom of navigation under the UNCLOS framework.
Maritime chokepoints concentrate risk, meaning that a localised disruption can cause a global economic shock. As globalization increased interconnection, and interconnection turned into interdependence, these waterways became at the same time strategically important and systematically vulnerable to geopolitical tensions.
The structure of maritime global trade is built on efficiency: in normal conditions, maritime chokepoints reduce transit times and logistic costs, working as conduits of the world’s seaborne commerce. However, efficiency comes at the expense of security and these corridors are turned into bottlenecks whose structural fragility States can exploit.
In this context, freedom of navigation is being challenged. When States can control who can access international straits, disregarding the right to transit passage without relevant repercussions, a dangerous precedent is set and it risks undermining UNCLOS authority as the constitution of the oceans. As predictability is replaced by uncertainty, legal standards can be reinterpreted by States in a way that it is consistent with their strategic interests.
The tension between legal principles and geopolitical realities is testing the boundaries of the convention, revealing a widening gap between norms and enforcement. By exploiting legal loopholes, States are redefining threat perception and raising the threshold below which maritime coercion is tolerated and unlikely to trigger a correlated or fragmented intervention. From this point of view, hybrid warfare is likely to become even more appealing because it enables States to exercise economic and political pressure while remaining within that threshold, leveraging not only what the law allows, but also what it does not clearly regulate.
UNCLOS is neither the problem nor the solution
Real world power dynamics between States limit UNCLOS efficacy; however, UNCLOS is neither the problem nor the solution to the uncertainty of the global maritime order. The question here is not whether UNCLOS remains fit for its purpose when it comes to maritime chokepoints; rather, it is about how to ensure that the transit principle is upheld even under growing geopolitical tensions.
The risk of non-compliance and the lack of centralized enforcement mechanisms are not exclusive to the law of the sea, but inherent characteristics of international law in many areas. Therefore, the solution to the problem can be neither a new treaty nor a revision of the convention, as the practical limits would remain unchanged.
Ensuring that transit through maritime chokepoints takes place in compliance with the legal provisions will ultimately depend on States’ ability to coordinate enforcement through practical cooperation mechanisms external to the UNCLOS framework, such as information sharing, satellite surveillance, joint training, and capacity building. Initiatives could involve a combination of formal and informal agreements between States, aimed at enhancing maritime security and responding flexibly to new threats at all levels. Nevertheless, such a strategy involves important trade-offs: while it has the potential to strengthen enforcement in the short term, it poses the risk of increasing the complexity and fragmentation of maritime governance. In fact, without a coordination mechanism within the UN system, a multilayered mechanism of initiatives risks turning counterproductive and further undermining the stability of the legal framework they are supposed to support.
In a multipolar and ever changing world where freedom of navigation is the backbone of global maritime trade, guaranteeing navigation rights in maritime chokepoints will depend less on past formal legal frameworks and more on new coordination and cooperation mechanisms that enable States to effectively address the gaps between UNCLOS legal provisions and their enforcement, mitigating risk and safeguarding mutual economic interests.
Conclusion
Politics, strategy, and international trade all converge in a small number of maritime chokepoints, where geography is increasingly leveraged to project power and maintain deterrence. The Straits of Hormuz crisis highlights the growing complexity of maritime governance in these narrow waterways, revealing an expanding divide between the letter of the law and its application in practice. UNCLOS continues to remain the foundational framework for maritime regulation, but its efficacy ultimately depends on States’ willingness to uphold the law in the light of emerging geopolitical tensions. As hybrid warfare, selective compliance, and reinterpretation test the limits of the UN Convention on the Law of the Sea, new forms of cooperation between States are necessary to ensure effective freedom of navigation in maritime chokepoints.
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