I have never dealt with this supplier but your comment (FQ-BB) makes no sense at all. Why do you state your language is english when you are clearly not a native english speaker?
"Precursor chemicals are licensed by the police from the factory to the sale"
What does this even mean?
Many chemicals that can be used for the manufacturing of drugs are sold freely, because they are not regulated. because they have never been a problem before, as time goes on these chemicals get regulated and prohibitated, and thereby stops being offered, just like with APAAN and MAPA (EAPA) etc etc and ofcourse the now controlled and regulated glycidates (BMK and PMK).
China, whilst it is not what we classify as a "democracy" still have rules and laws and people are not prosecuted for selling things that are not "illegal" (ergo they are legal until they change the laws),
Would you like to know which precursors are classified in china?
Here you go!: (signup to view them all, it's free). Enjoy the spoonfeeding.
Related catalogues of precursor chemicals include the Catalogue of Classifications and Categories of Precursor Chemicals, the Catalogue of Precursor Chemicals Subject to Import and Export Administration, and partial content of the Catalogue of Dual-Use Items and Technologies Subject to Import...
www.chemradar.com
(Again, I have never dealt with precursor supplier so I am not "with" anyone)