The use of the word "illegal" seems problematic if this is a contractual dispute over (GPL) license terms. No one
seems to be claiming that TikTok actually committed a criminal act (although, perhaps they did, if this was intentional as it appears, and TikTok is engaging in criminal-levels of distribution. Not a lawyer, so just speculating here.)
It probably would have been better if the OP had said "violated the license agreement".
Still, many other companies have eventually caved under GPL lawsuits, but apparently none in China; probably because it's virtually impossible as a foreigner to win a tort case against a Chinese company.
https://wiki.fsfe.org/Migrated/GPL%20Enforcement%20Cases