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Prioritizing the Marine Environment:
A Possible Malaysian Recharacterization of the Strait of Malacca to Regulate the Passage of Nuclear-Powered Submarines

By Mohd Hazmi Mohd Rusli
Published on 7 August 2023


Maritime traffic passing through the Straits of Malacca and Singapore, two of the world’s busiest shipping ways, has been consistently increasing over the years. With the rise of China’s military capacity against the might of the forces of the United States and its allies, passage of military vessels via these crucial straits is anticipated to increase, including passage of nuclear-powered submarines. As the main maritime conduit connecting the Pacific Oceanvia the South China Seato the Indian Ocean, the significance of this maritime link is indisputable.

Nuclear-powered submarines flying Chinese and Indian flags have been reported to have traversed the straits in recent years. With the adoption of the security pact between Australia, the United Kingdom, and the United States (AUKUS), Australia will be the next country in the region to possess nuclear-powered submarines by 2040. Therefore, it is not unrealistic to expect that the Straits of Malacca and Singapore will potentially accommodate increasing number of nuclear-powered submarines in coming years. This has been a concern of Malaysia.

So far, there have been eight  incidents of sunken nuclear submarines worldwide, either by accident or scuttling, and all of them in the Atlantic and Arctic Oceans. The Soviet and Russian Navies lost four and two nuclear-powered submarines, respectively; while the United States’ Navy lost two. Unlike other types of vessels, these sunken nuclear submarines may threaten the marine environment by leaking radiation into the sea, affecting it permanently. Radioactive waste in the ocean can affect global fish migration, fisheries, human health and ecological security. While Southeast Asian waters have not experienced such incidents, the collision of the United States nuclear-powered submarine with an unknown underwater object in the South China Sea in 2021 have led to fears of potential nuclear disaster in the region, including the busy waters of the Straits of Malacca and Singapore. Therefore, this potential increase of traffic involving foreign military vessels, particularly nuclear-powered submarines, may threaten the marine environment and security of the littoral States.

To remedy this situation, this essay proposes that a solution could be to review the application of transit passage regime under Part III of the 1982 United Nations Convention on Law of the Sea (UNCLOS) for maritime navigation of nuclear-powered submarines. Consequently, Malaysia could unilaterally declare that as far as navigation is concerned, the Straits of Malacca and Singapore are not part of the same strait, thus recharacterizing the position as straits where transit passage applies.

Navigational rights of foreign vessels were a significant issue addressed during the third United Nations Conference on Law of the Sea, that took place in 1970s. As the innocent passage regime allows coastal States to temporarily suspend passage of foreign vessels in the territorial sea, maritime States have insisted on a different regime to be applied for straits used for international navigation. As a quid pro quo of extension of territorial sea limits from 3 nautical miles to 12 nautical miles, transit passage was then acknowledged as the regime applicable to foreign vessels navigating international straits under UNCLOS. Article 44 of UNCLOS mentions that States bordering straits shall not hamper or impair navigation. This has hampered such States’ maritime regulatory capacity, including that of Malaysia.

From a geographic perspective, without the Strait of Singapore, the Strait of Malacca could be viewed as a strait that connects one part of the high seas or an exclusive economic zone to a territorial sea of a third State. This would fit the definition under Article 45(1)(b) of UNCLOS of a strait in which non-suspendable innocent passage applies. If Malaysia unilaterally declares that the status of the strait has changed, Kuala Lumpur could contend that the navigational regime of non-suspendable innocent passage would apply in the Strait of Malacca. This would mean that transit passage would cease to apply, which would in turn mean that nuclear-powered submarines would no longer be allowed to navigate in normal mode because these vessels are required to surface under the regime of non-suspendable innocent passage.

In addition, Article 45(1) of UNCLOS stipulates that the application of non-suspendable innocent passage shall be subjected to the rules of innocent passage underlined in Part II of UNCLOS. Under this navigational regime, Malaysia could also apply the provision of Article 30 of UNCLOS that empowers coastal States to suspend navigation of recalcitrant naval vessels. The application of this provision would put these States in a better position to protect their maritime sovereignty, a right that is not available under the regime of transit passage. This reinterpretation or recharacterization would also nullify the application of Article 42(1)(a) and (b), Article 42(2), and Article 44 of UNCLOS, which disallow States bordering straits to implement regulations that could impede navigation. However, this does not in any way mean that the littoral States can suspend the passage of vessels navigating the Strait of Malacca without any valid or compelling reason to do so. Unlike the innocent passage regime in the territorial sea, vessels exercising non-suspendable innocent passage are not subjected to suspension, as the name of this regime implies.

It is acknowledged that this reinterpretation of the navigational regime applicable in the Strait of Malacca would be highly contentious among maritime States like the United States, the United Kingdom, China and, of course, Malaysia’s closest neighbour, Singapore. It is likely that such a declaration would be rejected by most maritime States, and that they would argue that the regime of transit passage in the Strait of Malacca had achieved the status of customary international law. Closing important maritime highways to vessels carrying hazardous nuclear substances would, one way or another, violate the spirit of UNCLOS that guarantees unimpeded right of transit passage for vessels via straits used for international navigation.

However, it could also be argued that Article 192 of UNCLOS places an obligation on each State Party to protect and preserve the marine environment within or beyond national jurisdiction. The importance of the respect of this obligation can be seen in several decisions taken by the International Tribunal of Law of the Sea (ITLOS). For instance, the 2003 judicial pronouncement of ITLOS on the reclamation works around Pulau Tekong was aimed at both Malaysia and Singapore to jointly cooperate for better coordination and environmental management of the eastern region of the Johor Strait. Small island States have also resorted to ITLOS for an advisory opinion with regards to climate change and sea level rise. Earlier in June 2023, the so-called ‘High Seas Treaty’ was adopted by the United Nations to safeguard the marine environment beyond national jurisdiction against environmental degradation arising out of prospective deep-sea mining activities.

Bearing this in mind, UNCLOS must therefore be able to balance navigational rights and protection of the marine environment following latest developments. Treaties such as UNCLOS are not static and are subject to legal evolution and reinterpretation. UNCLOS was drafted in the 1970s when there were not as many nuclear-powered submarines transiting the seas as there are today. Although it may be controversial to legally recharacterize the Strait of Malacca, it may not entirely be unrealistic.

The assertion that the replacement of the transit passage regime with non-suspendable innocent passage would hamper international maritime traffic passing through the straits is flawed. Vessels and ships would continue to enjoy non-suspendable innocent passage through the Strait of Malacca. As stated earlier, the application of this navigational regime would neither impede nor hamper free passage of shipping because there is no right of suspension. Nevertheless, via this new legal reinterpretation, Malaysia would be able to act against recalcitrant naval vessels in the Strait of Malacca, as provided in Article 30 of UNCLOS.

Any attempts to reinterpret the existing navigational regime must not have the practical effect of denying or impairing passage of vessels genuinely exercising passage through the Straits of Malacca and Singapore. The term ‘genuinely exercising passage’ refers to navigation of ships solely for the purpose of transit without any intention to undermine interest or security of States bordering straits.

The preamble of UNCLOS clearly promotes ‘peaceful uses of the seas and oceans’ and ‘preservation of the marine environment’. Thus, the navigational regime of vessels carrying hazardous substances, such as nuclear-powered submarines, should be reinterpreted to further protect the interests of States bordering straits and the international community.


Mohd Hazmi Mohd Rusli is Associate Professor at the Faculty of Syariah and Law, Universiti Sains Islam Malaysia and Research Associate at the Asian Institute of International Affairs and Diplomacy, Universiti Utara Malaysia. He recently completed his maritime fellowship at Australian National University, Canberra in 2022.