So this new security law. Wow, I'm not sure it could have been more unfocused and wide-ranging. It even grants Chinese state security immunity from being detained or even have their vehicles searched. So if they arrest the wrong person or accidentally kill someone during an interrogation, they just need to waive their badges, say they were performing official duties and it's all good. (Before anyone says action could be taken in the mainland courts, yeah good luck with that).
Hell, given their vehicles can't be searched, they can now kidnap people and take them over the border without worry about being stopped by the HK police. They don't even need to bother with the new law. Or they may use that right in conjunction with the procedure to take suspects for trial in mainland China to "save time" if they want to try to avoid publicity for as long as possible.
The Hong Kong Bar Association has a fairly good critique of the new law. For a start the offences are incredibly vague. In particular I thought this point was especially good:
So anyone who receives money from overseas - even if through a legitimate and peaceful NGO - could be prosecuted if the CCP or HK government decides that their work is "hostile". There is no reference to having to be violent. "Hostility" can be peaceful or lawful. Opposition parties are hostile towards incumbant governments because they oppose government policies and seek to impliment their own manifestos.
The scope of the new legislation isn't just terrorism, it clearly can cover opposing the HK government in what until now were legitimate and legally-protected ways. Indeed, this smacks of Singapore's laws where the government can silence anyone that criticises it too strongly or in a way that's embarrassing.