Sen. John McCain, R-Ariz., chairman of the Senate Armed Services Committee

[UPDATED with experts’ analysis; “innocent passage” confirmed] WASHINGTON: Just two days after the head of US Pacific Command, Adm. Harry Harris, pledged to push harder on Chinese territorial claims in the South China Sea, the destroyer USS Curtis Wilbur sailed within the 12 nautical mile limit around Triton Island. Situated in the Paracels, which are claimed by China, Taiwan, and Vietnam, Triton is one of those islands China seized from what was then South Vietnam in a 1974 offensive that left at least 70 Vietnamese dead. Today, the Paracels are a potential flashpoint in ongoing disputes over the potential oil and gas wealth of the South China Sea. (It’s also worth noting that they’re real, natural islands rather than the artificial constructions of Chinese engineers).

Senate Armed Services chairman John McCain and House seapower subcommittee chairman Randy Forbes, who have criticized the Obama Administration for letting China run roughshod over our friends and allies in the South Pacific, praised the operation — somewhat grudgingly in McCain’s case.

USS Curtis Wilbur

“I am encouraged to hear that the U.S. Navy has conducted a freedom of navigation operation near Triton Island in the Paracel Islands in the South China Sea,” Sen. McCain said. “This operation challenged excessive maritime claims that restrict the rights and freedoms of the United States and other nations under international law. I continue to hope these operations will become so routine that China and other claimants will come to accept them as normal occurrences and releasing press statements to praise them will no longer be necessary.”

“By sailing within the disputed waters around Triton Island,” said Rep. Forbes, “the men and women of the USS Curtis Wilbur have sent a strong signal of America’s enduring commitment to Asia and the rule of law.  While the ownership of these islands may be in dispute, the right to freely fly, sail, and operate in the surrounding waters is not. I am pleased that we seem to have resumed exercising and demonstrating that right on a routine basis. I urge the administration to continue conducting freedom of navigation operations, and I call on other maritime nations to stand up for our shared rights and join us in freely exercising them.”

Rep. Randy Forbes

What’s the backstory at which McCain and Forbes are hinting? While the US emphatically takes no position on who owns what islet, rock, or reef in the South China Sea, it does dispute Chinese claims to a “territorial sea” extending 12 nautical miles from various natural features and artificial islets that Beijing considers its sovereign territory. But the Pentagon admitted last year that it had stopped sending ships and aircraft within the 12-mile limit in 2012.

Last fall, after months of public statements, confusion, and delay, the destroyer USS Lassen ended the three-year hiatus in such “Freedom Of Navigation Operations” by cruising within 12 nautical miles of Chinese-claimed Subi Reef. It did so without giving notice to or asking permission of Beijing, violating the Chinese interpretation of international law. However, by most interpretations of international law, Lassen simply conducted an “innocent passage” — sailing straight through the contested waters without engaging in specifically military operations — which warships of one country may freely do in the territorial waters of another.

What is forbidden in another country’s territorial sea is specifically military activities — even something as simple as launching a helicopter or turning on a targeting radar. Critics say that only conducting such military operations within the 12-mile limit would constitute an unequivocal statement that, as far as the US is concerned, these are not Chinese territorial waters but part of the “high seas” on which any nation may do as it likes.

The Pentagon said in a statement that “the USS Curtis Wilbur, (DDG 54) transited in innocent passage within 12 nautical miles of Triton Island” — which means it did not conduct military activities. So how serious a challenge was the operation to China’s claims? Patrick Cronin, Asia-Pacific director at the Center for a New American Security, told me that “the US is compounding the problem by making China think the US is not serious.”

“The US isn’t really challenging any Chinese maritime claims, and in fact is helping to support them by conducting an innocent passage, which is allowed within 12 miles of someone else’s territory,” said Bryan Clark, a former top aide to the Chief of Naval Operations. “If the U.S. wanted to challenge China’s and other’s claims, the ship would conduct ‘military operations’ such as running radars or conducting helo ops. It did not do this.”

“Interestingly,” Clark added, “Taiwan and Vietnam are not protesting, because they recognize an innocent passage as being allowed under UNCLOS, even if the territory is theirs.” Only China is protesting, based on its historical sensitivity over sovereignty and its broad interpretation of its territorial rights under international law.

In its limited scale, the Wilbur operation is essentially a repeat of the Lassen‘s. “This is not a ratcheting up from the USS Lassen FONOP in October,” said Bonnie Glaser, director of the China Power Project at the Center for Strategic and International Studies. “It is a resumption of the FONOPS that used to take place [before 2012].”

“To ‘up the ante,’ the US needs to conduct a FONOP around Mischief Reef,” Glaser said. At least by the US interpretation of international law, Mischief Reef is not an a land mass entitled to territorial waters, but merely a “low tide elevation,” completely submerged at high tide, and therefore entitled only to a 500 meter safety zone. What’s more, Mischief is the only Chinese-occupied territory in the South China Sea that is further than 12 nautical miles from any other feature and therefore outside any other place’s territorial waters. (By contrast, Glaser said, Subi Reef — which Lassen passed last fall — was within 12 nm of a feature classified as a “rock” and thus arguably within that rock’s territorial waters).

“Therefore,” said Glaser, “if the US demonstrates freedom of navigation near Mischief Reef, it will have to go beyond ‘innocent passage’ and conduct a military operation, such as turning on radar or flying a helicopter inside the 12 nautical miles. Since the Chinese are rapidly building facilities on Mischief Reef that have potential military uses, this should be the next target of a US FONOP in the South China Sea.”

We’ll see if Admiral Harris and the White House take her advice. So far details from the Pentagon are sparse:

“This operation was about challenging excessive maritime claims that restrict the rights and freedoms of the United States and others, not about territorial claims to land features,” said a Defense Department statement. “The United States takes no position on competing sovereignty claims between the parties to naturally formed land features in the South China Sea. The United States does take a strong position on protecting the rights, freedoms, and lawful uses of the sea and airspace guaranteed to all countries, and that all maritime claims must comply with international law.”

The Chinese have already denounced the US move, unsurprisingly:

“The US.naval ship violated Chinese law to enter China’s territorial waters. China monitored the ship’s movement and issued verbal messages in accordance with law,” said a Foreign Ministry spokesperson. “We urge the U.S. side to respect and abide by relevant laws of China, and do more to improve mutual trust as well as regional peace and stability.”

Said Clark, “China’s reaction is part of their public relations campaign to maintain a level of nationalistic fervor about challenges to its maritime claims. They want the issue to remain in the Chinese public conversation, but not be so much an issue it tips over to ‘wag the dog‘ and cause the government to have to actually respond militarily to US [freedom of navigation] ops.”

“In international law, how a nation treats a perceived violation of its territory is important,” Clark continued. “”If the victim fails to protest the violation, eventually a precedent is set that the territory is not necessarily the claimant’s. Therefore, I would expect continued protests from China to help sustain their claim.”