Last Friday, on the heels of Philippine President Rodrigo Duterte declaring his “separation from the United States” during a visit to China, the USS Decatur conducted a freedom of navigation operation (FONOP) in the vicinity of the Paracel Islands in the South China Sea. Julian Ku has written about this operation here. The Paracels are currently occupied by China and also claimed by Vietnam and Taiwan (though not the Philippines). As Julian describes, the apparent purpose of the U.S. FONOP was to challenge China’s “straight baselines” around the entire Paracel Islands group, which China publicly declared in 1996 and the legality of which the United States has long contested.

Reuters and the Navy Times cite anonymous U.S. officials who say that the ship did not patrol within 12 nautical miles of any of the Paracel Island features. It did, however, sail into waters China claims as its territorial seas. A statement from the Chinese Foreign Ministry denounced the action as “illegal” and “provocative,” and asserted that the U.S. had not asked for permission to enter China’s “territorial waters.” A Pentagon spokesman said the Decatur had “conducted this transit in a routine, lawful manner without ship escorts and without incident…specifically in the vicinity of the Paracel Islands, to uphold the rights and freedoms of all States under international law, as reflected in the Law of the Sea Convention.”

Based on these accounts, as Julian explained, the U.S. FONOP presumably did not follow the rules of “innocent passage” through a country’s territorial sea. This is because the United States objects to the notion that the waters it transited are in fact territorial seas under international law, as established in the United Nations Convention on the Law of the Sea (UNCLOS).

To understand the implications of this mission, it is worth stepping back to consider the diplomatic and legal context.

https://www.lawfareblog.com/vietnam-unclos-tribunal-and-latest-us-fonop-south-china-sea