i don't think vietnam are using international law in this matter regarding its claim. if international court find in favor of ph, do you thing vietnam will just give up, i doubt it. there are many incidents where china/vietnam/ph/mala harasing each other, all has historical records etc etc say SCS is theirs.Overlapping yes but both are not trying to outdo one other and both are willing to use international law so that problem as at less a solution while china likes to claim all even the waters which is illegal in international law