There is the freedom of passages for both merchant & warships in any seas or oceans. In my opinion, no reason for objecting the PLA-N from conducting exercises or patrolling the Western Pacific; or the Japanese, Korean Navy or any Navy for that matter from sailing into the South China Sea and surrounding waters. As for facilities, it's up the the countries concerned whether they would want to provide such facilities to the USN. After all, Pakistani ports in the Indian Ocean have reportedly provided the PLA-N with berthing and fuelling facilities. In this day and age, we look at development of trade ties among countries & one should avoid belligerancy by any military or naval leaders.
OK, advill, hold it there. The "freedom of passages ... for warships" means PASSAGE, not "drills" or "patrolls". You bet a freindly (or at least "innocent") navy passage through US water will became unfreindly very quike, if they starting to "drilling" things, and uncle sam would put them to a stop before anyone hurts / further hurts himself.
That's what
sovereignty water means, and I see no different if it's SCS we are talking here.
- Yes, even to a certain extends, there's "disputed" sovereignty water among China and few others (and among those few others themselves), I don't see justification if Japanese, S.Korean, or even American navy start to do anything more than PASSAGE throughout the area. - And China never deny or hamper (or like
some likes to do - tailing), those who innocently PASSING the area, merchant or warships.
And again, FYI, US didn't sign the UNCLOS, which people have the right -
well, have not the capability it turns out - to deny USN's passage, through their own sovereignty water. Something, let's say, US as a nation, should cherish for - at least in a diplomatic level.