UNCLOS III provides that, if a ship or its crew are seized on the high seas, the flag state can appeal to the International Tribunal for the Law of the Sea (ITLOS) in Hamburg, Germany, for a prompt decision on the legality of the seizure.³ The treaty allows states to opt for other forms of arbitration on other disputes, but other forms of arbitration require all nations involved to agree on a specific panel of arbitrators. The only important category of dispute where one party can force another to answer before ITLOS is when a ship has been detained on the high seas and the complaining party seeks its immediate release.

Seizing a ship on the high seas without the consent of its home government would inevitably trigger a diplomatic confrontation. But in the right circumstances, the United States or its allies might feel obliged to act first and try to handle the diplomatic protests later. If intelligence gives reasonably firm indications of an imminent terror attack to be launched from a particular ship, the U.S. could insist on intervening, claiming a right of self-defense that supersedes the general “rules of the road” at sea. Alternatively, the United States might claim that a ship operated by terrorists was so closely analogous to a pirate ship that intervention could be justified under the UNCLOS exemption for piracy. In still another variant, the United States might interpret a bilateral agreement with the flag state as covering a particular intervention, while the flag state insisted on a different interpretation. In any of these cases, the flag state would likely sit on the sidelines while the ship’s operators pursued a claim on their own initiative, “on behalf of the flag State,” as UNCLOS allows.⁴ It is easy to imagine situations in which U.S. intervention might trigger a complaint to ITLOS. It is hard to imagine situations in which ITLOS would be other than a complicating factor in ensuing U.S. diplomacy toward the flag state.