The world's oil, gas, grain and manufactured goods are concentrated in a handful of narrow straits. They are protected by the regime of transit passage under the 1982 United Nations Convention on the Law of the Sea (UNCLOS) that cannot be suspended or obstructed by the coastal states. That guarantee has been tested in 2026 with the closure and conditional reopening of the Strait of Hormuz, and the attacks on the Red Sea started in late 2023. In this paper, the author considers whether passage through a strait is now customary international law that binds states outside UNCLOS, and if a coastal state may use Article 51 of the UN Charter to justify closing a strait. It also raises questions about the remedy available in neutral states, especially in the Global South, for indirect economic harm. In doctrinal analysis of ICJ jurisprudence and a global justice perspective, I claim that the core rule of transit passage is customary and that it can never be suspended, and that any limitation of a transit passage in armed conflict must be necessary and proportional.