After the war, there is no future for multilateralism without freedom of navigation

The author is a professor of law at the Seoul National University's School of Law. "Like a lifeboat in the dark." That was how an astronaut looking back at Earth from NASA's Artemis II mission described the planet, the only apparent home for life in the vast sea of space. In that calm blue image, the wars and conflicts unfolding across the world seem to overlap in a single frame. The value of the Strait of Hormuz has been revealed with unusual clarity in the current war. The conflict may have begun over nuclear weapons, but global attention has settled on the strait. That shift alone shows how decisive the issue of maritime passage has become. Rules governing the sea stood at the starting point of modern international law some 400 years ago, when trade and contact between states depended overwhelmingly on sea routes. From that history emerged a basic principle: no state owns the sea, and all states enjoy freedom of navigation. That principle was reaffirmed in the 1982 United Nations Convention on the Law of the Sea and remains central to maritime order today. New rules have developed for exclusive economic zones and the use of marine and seabed resources, but the principle governing passage itself has remained remarkably firm. That cornerstone is now being shaken. Threats to ships evolved into demands for payment, and then into blockade-like restrictions. Transit fees on a natural strait are strange enough. More unusual still is the sight of two countries at war moving at the same time to restrict the same maritime space. Since openly defying maritime law would be burdensome, legal justifications have followed. The law of the sea prohibits the imposition of tolls in straits. Artificial waterways such as the Panama and Suez canals can charge fees, but natural passages cannot. There is a narrow exception: If a state provides special services to passing vessels, it may collect payment for those services. Iran has seized on that point, arguing that it provides safety and environmental services to ships transiting Hormuz and should therefore be paid. The proposed charges, however, look very much like tolls in another form. The United States has offered a careful explanation of its own. It says it is not blocking the strait itself but controlling vessels entering and leaving Iranian ports. The ports are restricted, it argues, while the strait remains open. That distinction appears designed to avoid the legal consequences of closing an international strait. Yet in practical terms, the difference is hard to see. For now, all this is happening in wartime. Whether these measures are called tolls or blockades, one might accept that extraordinary means are being mobilized in a conflict seen as existential. The real concern begins after the war ends. There is reason to fear that some form of control over the strait could quietly take root even in peacetime. A chokepoint of such geopolitical value is unlikely to be left entirely untouched by neighboring states or great powers. Direct tolls or formal blockades may prove too visible. Instead, more subtle "managed barriers" could emerge in the name of safety, security, the environment, resources or public health. In time, those measures could lead to selective passage. If that barrier breaks once, the spread of similar practices to other maritime chokepoints may be only a matter of time. Even now, about 80 percent of global trade moves by sea, much of it through eight major chokepoints. The weaponization of resources is an old story. Now sea lanes themselves are joining that list. That is more dangerous. Resources involve goods that belong to particular states. Sea lanes are public goods used by all. Blocking a commodity disrupts one sector. Restricting sea lanes shakes the entire trading system. Some propose alternative routes. Others suggest more undersea cables and pipelines. But those, too, are vulnerable to the influence of nearby powers and to external attack. They are not a fundam...