As David Bosco hinted in his insightful Lawfare post from yesterday on the US-China showdown in the South China Sea, it turns out that the much-heralded U.S. “freedom of navigation operation” (FONOP) last week in the South China Sea was conducted according to the rules of “innocent passage.” As I will explain below, this approach is the weakest type of FONOP the U.S. could have chosen. And to make matters worse, limiting the FONOP to innocent passage could actually strengthen China’s sketchy territorial claims in the region.

As the US Navy confirmed yesterday, the USS Lassen’s FONOP near the Chinese artificial island on Subi Reef in the South China Sea was conducted as an “innocent passage.” This means that the Lassen’s transit within a 12 nautical mile zone around the Chinese artificial island was conducted consistent with the definition of “innocent passage” in Article 19 of the UN Convention on the Law of the Sea (UNCLOS). As a practical matter, this means that the Lassen suspended its military capabilities while in the 12 nm zone. Hence, the US Navy reports the Lassen’s fire control radar was shut off and it flew no helicopters. Other naval aircraft stayed out of the 12 nm zone because there is no right to innocent overflight by military aircraft in another country’s territorial sea.

Reports further suggest that the White House chose the “innocent passage” FONOP out of a menu of options presented by the US Navy. It perhaps is not surprising that the White House chose the least confrontational option. Although China’s government and state media have been predictably hyperbolic in their response to the Lassen’s FONOP, the actual dispute with China boils down to a pretty technical legal quibble over which ships can invoke the right to innocent passage under UNCLOS. The US reads UNCLOS as allowing all ships, including military ships, to enter into a territorial sea (defined as 12 nautical miles from land). China reads UNCLOS as limiting innocent passage to civilian ships and thus, China requires military ships to get permission before entering their territorial seas, even for “innocent passage.” (I have a description of this legal dispute here).

This difference in legal interpretations is not trivial, but it hardly goes to the heart of the US government’s concerns about China’s island-building in the South China Sea. Why? Because by limiting the USS Lassen’s transit to an “innocent passage,” the U.S. is implicitly recognizing that China is entitled to a 12 nm territorial sea around its artificial island on Subi Reef.

But the U.S. (along with many other nations) has criticized China heavily not just for island-building (which in itself is not a violation of UNCLOS), but for claiming territorial seas based on artificial islands (which is clearly inconsistent with UNCLOS Article 60). More precisely, the U.S. does not believe China can build an island on top of a land feature that can sustain neither human habitation nor stay above sea level at high tide. Under UNCLOS, a land feature that lacks these qualities cannot generate rights to a 12 nm territorial sea.

There is little doubt that Subi Reef, the land feature that was the subject of the USS Lassen’s FONOP, is neither a rock nor an island under UNCLOS. No one, not even the Chinese, have really claimed otherwise. So why was the U.S. so careful to limit the USS Lassen’s transit to an “innocent passage” FONOP? Doesn’t this mean the U.S. Navy is implicitly recognizing that China has a 12 nm territorial sea?

The most likely reason for the “innocent passage” FONOP is that it is the least likely to ruffle Chinese sensibilities. That may or may not be a good idea, although I haven’t really seen any restraint in official Chinese rhetoric on this subject. I hope the good folks at the White House have also thought through the rest of their strategy, which will likely bolster (rather than undermine) the dubious Chinese territorial claims that are at the heart of the problems destabilizing the South China Sea.