Patent regimes are territorial. If you don't patent in the Chinese jurisdiction they can do whatever they want over there. Same for other industrialised nations where you have not applied for a patent.
The opinion of the Advocate General is a preliminary document, a recommendationn, not a ruling of the Court. A recommendation to the European Court that is often followed by the Court. Legal grounds is the current EU directive, a directive that is implemented in national laws and provides a level of minimum harmonisation across EU member states. There may be other legal grounds. Currently the entire EU data protection legislative framework is under reform.