Chinese propaganda operating freely in the west platforms, while western propaganda being filtered in Chinese platforms is a real conundrum since both parties are... following relevant local regulations. I suppose labeling state actors and revealing misinformation campaigns is a start. The other insidious strategy is suppressing speech on foreign campuses that target foreign citizens, particularly anti-China advocates who can be coerced with threats to family back in China. No real good solution except punishing obvious bad actors. Maybe ban children of CCP officials from attending these institutions if they can stomach the retaliation in withdrawn Chinese enrollment. Censorship between US and Chinese platforms are a difficult structural asymmetry. Hard to see how west can match without adopting similar (anti)values. Not much to do but mitigate.
On your examples: CCP sees some speech as national security issues, which in itself is not controversial i.e. wikileaks. On Luo Daiqing in, countries have subject matter jurisdiction, laws that apply to citizens at all times and regardless of location, i.e. treason. If certain speech is outlawed in China then Chinese nationals can legally be prosecuted by China for them regardless of jurisdiction. Other countries have same legal arrangements on other issue, i.e. sex tourism, organ transplants, drug use. Causeway Books is more complicated, HK(Chinese) and foreign nationals operating in HK to distributed banned books to customers IN mainland which is illegal but also un-prosecutable due to lack of extradition treaty with HK. Basically the reason behind current HK national security law designed to close one-country security loopholes. CCP believes selling illegal books to mainland undermines national security. It was less of a free speech issue than shenanigans comparable to foreign NGO meddling that CCP thinks jeopardizes one-country national security and worth expending political capita on to control. Since national security in context of one-country was legally undefined, CCP was forced to resort to coerce or rendition. It's like how the west will prosecute whistleblowers wherever they are, sometimes through extraordinary means, no matter the optics. Even though in this context the book sellers were (from my understanding) peddling salacious gossip.
On your examples: CCP sees some speech as national security issues, which in itself is not controversial i.e. wikileaks. On Luo Daiqing in, countries have subject matter jurisdiction, laws that apply to citizens at all times and regardless of location, i.e. treason. If certain speech is outlawed in China then Chinese nationals can legally be prosecuted by China for them regardless of jurisdiction. Other countries have same legal arrangements on other issue, i.e. sex tourism, organ transplants, drug use. Causeway Books is more complicated, HK(Chinese) and foreign nationals operating in HK to distributed banned books to customers IN mainland which is illegal but also un-prosecutable due to lack of extradition treaty with HK. Basically the reason behind current HK national security law designed to close one-country security loopholes. CCP believes selling illegal books to mainland undermines national security. It was less of a free speech issue than shenanigans comparable to foreign NGO meddling that CCP thinks jeopardizes one-country national security and worth expending political capita on to control. Since national security in context of one-country was legally undefined, CCP was forced to resort to coerce or rendition. It's like how the west will prosecute whistleblowers wherever they are, sometimes through extraordinary means, no matter the optics. Even though in this context the book sellers were (from my understanding) peddling salacious gossip.