The PCA "rulings" aren't international law because UN (which PRC accept as international system) has no formal position on them / has not adopted any parts of the decision. Ergo, PRC's SCS position is consistent with international law - like the actual one at UN, not make believe US "rules based order" which was behind PCA lawfare campaign and the ongoing propaganda.

PRC is more firmly within bounds of the "world system", versus US who tries to enforce FONAPs despite not ratifying UNCLOS, and doesn't respect the kind of international law that it accused PRC of violating, see ITLOS ruling (an actual UN ruling) regarding UK/US military base on Chagos/Mauritius/Diego Garcia.