joshuatree
Captain
The US hasn't signed UNCLOS, but she does observe the rules and statues. Rear Admiral James Foggo recently visited China and reported that he was pleasantly surprised the Chinese government recognizes US observance of UNCLOS, even though it hasn't signed the treaty. In his words, it wasn't a big deal with Chinese leaders.
So what prevents the US from signing if so closely aligned?
As you say, UNCLOS doesn't stipulate whether it's legal or illegal to spy in international waters, so there's room for interpretation. However, if the majority of major countries see things one way, then that's the norm. If some nations believe the 'norm' is wrong, then they'll be smart to take it to the International Court of Justice and get a favorable ruling.
The same ICOJ the US brushed off when it ruled against the US in a case vs Nicaragua? As I pointed out, when Chile and Peru first established the 200 nm EEZ, that was not the norm. Somehow, it is now. Who's to say spying within the EEZ is considered a provocative, nonpeaceful act, by the majority of nations in the future? And being that there's room for interpretation, it's a little overkill to be labeling the opposition as fantasy reading.
You are quite right, and the US is rather happy China is spying off Guam and Hawaii. In fact, Admiral Locklear, Commander of US Pacific Command, was quoted in news media as welcoming Chinese ships off US shores gathering intelligence.
The US is happy because it believes this will affirm their right to spy in other's EEZ. But time will tell if the welcome stays when China gets more sophisticated and develop longer sea legs and better sensors, when it will routinely have such activities up and down the West coast, East coast, Gulf of Mexico, Alaska. Or when China starts to do this in other US ally's EEZ, I certainly hope the US will not come out saying it's aggressive and raises tension but say "Welcome, please spy on them for it is the norm. To the US ally country, you need to be quiet because it is the norm".