What the ruling does is to legitimize the tariffs that China applied on US goods.
A WTO ruling on invalidity of tariffs essentially does one thing: the party with the winning verdict can lawfully apply the same amount of tariffs back (which China has already done anyway).
So nothing really will change apart from the fact that US tariffs on China is now "illegal" under international law while Chinese tariffs on the US is now "legal". So China can say that its actions are within the framework of the rules-based international order and slam the US on that.
Basically at this point it's a moral weapon instead of doing anything in particular.
A WTO ruling on invalidity of tariffs essentially does one thing: the party with the winning verdict can lawfully apply the same amount of tariffs back (which China has already done anyway).
So nothing really will change apart from the fact that US tariffs on China is now "illegal" under international law while Chinese tariffs on the US is now "legal". So China can say that its actions are within the framework of the rules-based international order and slam the US on that.
Basically at this point it's a moral weapon instead of doing anything in particular.