There are numerous other articles about the issue.
Basically China has stated that they have the right to board and detain any ship that enters their territory illegally. By their territory they mean the vast majority of the South China Sea. This leaves them at odds with Japan, Phillipines, Thailand, Vietnam, Singapore...
What do you think the odds are that a Chinese military vessel attempts to stop a ship? What do you think the US Navy response would be to such an act.
Scenario: A large cargo ship is going from Thailand to Mexico. It passes thru international waters that China now claims as their own. No one else recognizes these claims. Well China stops the vessel and forces it to turn back. This is reported to a US Navy battle group in the area. Does the US let them go and basically acknowledge Chinese claims to the South China Sea in direct opposition to several key allies in the region such as Japan and the Phillipines? Or do they go in and engage/standoff with the Chinese milatry vesels to prevent them from stopping/confiscating the ship and its crew and cargo and risk war with China?