Why Does the U.S. Demand Innocent Passage in the South China Sea, But Not in the Persian Gulf?

The brief Iranian detention and safe return last week of 10 U.S. sailors – and their equipment – would seem to have little in common with ongoing U.S. plans for Freedom of Navigation Operations (FONOPs) in the South China Sea. But the failure of the U.S. to openly criticize Iran’s detention of U.S. ships could seriously undermine the U.S.’s ability to push back against China in the South China.

Why? Because reports from the U.S. Navy investigation of the incident strongly suggest that the U.S. ships detained by Iran were entitled to conduct “innocent passage” through Iran’s territorial waters under the principles codified by the U.N. Convention on the Law of the Sea. Under Article 19 of this treaty, military ships can traverse a territorial sea as long as its passage is “not prejudicial to the peace, good order, or security of the coastal nation.” Like the U.S., Iran has signed but not ratified UNCLOS. But Iran has acknowledged innocent passage is a principle of customary international law.

Iran has not claimed that the U.S. naval ships were acting in a threatening manner that would violate the “innocent passage” doctrine. Rather, Iran apparently believes that the U.S. ships were required to get permission before traversing their territorial waters, even if the transit was conducted under innocent passage.

Iran’s interpretation of the innocent passage doctrine finds little support under the text of UNCLOS and it has been squarely rejected by most major seafaring nations, including both the U.S. and the then-Soviet Union. Indeed, such a restrictive reading of innocent passage effectively undermines the whole purpose of the doctrine and it is inimical to the interests of the world’s largest naval power.

Conducting innocent passage in the territorial waters of nations (like Iran) who require permission is a common U.S. FONOP that the U.S. Navy believes upholds the broad principle of freedom of navigation. In 2014, the US Navy reports it conducted FONOPs under innocent passage in the territorial seas of Argentina, Indonesia, Nicaragua, South Korea, and Taiwan. The much-ballyhooed October 2015 U.S.S. Lassen FONOP in the South China Sea was – as discussed before here – an “innocent passage.” Yet China protested the operation on the grounds that the Lassen should have demanded permission before conducting a FONOP. [I’ve written more about that legal dispute here.]

So if the U.S. is willing to make the right to innocent passage a part of its FONOP program, why didn’t it challenge the legality of Iran’s detention? Perhaps the U.S. didn’t want to upset the negotiations that eventually won the U.S. sailors’ release – or unrelated negotiations related to the release of American prisoners from Iran days later. But now that the sailors are free, there should be nothing that prevents the U.S. from declaring – as Senator John McCain has done – that Iran’s seizure and detention violated international law and the principles of freedom of navigation. Nor is there anything that should prevent the U.S. from conducting an innocent passage FONOP in Iranian territorial waters.

I recognize the delicate state of current U.S.-Iranian relations. But the U.S. cannot allow this incident to set a precedent for other countries. What if China seized a U.S. vessel conducting innocent passage in its “territorial waters”? At the minimum, the U.S. should do far more to clarify whether it views the seizure and detention as legal. Leaving its position on this issue unsettled cannot help – and is likely to seriously hurt – its long-held commitment to uphold freedom of navigation.