It's explicitly illegal in China.

A 2017 national intelligence law compels Chinese companies and individuals to cooperate with state intelligence when asked and without and public notice.

China has no equivalent of the whistleblower protection that enables resignations with public letters explaining why, protests, open letters with many signatures, etc. Whenever you see "Chinese whistleblower" in the news, you're looking at someone who quietly fled the country first and then blew the whistle. Example: https://www.cnn.com/2026/02/27/us/china-nyc-whistleblower-uf...