Chinese law doesn't apply in HK. HK has its own border, passport, security, police, pplitics, driving, language, educatiin system. HK has uncensored internetz freedom of speech, free elections, freedom of religion, freedom of travel (no Hukou bullshit, and the passport isn't worthless), freedom of the press, right to protest, right to criticize the government, fsir trials when charged with a crime, no black jails or anything of that matter, must I go on?
It may "officially" be China's in name, but calling it China and treating it like every other part of the corrupt communist shithole is wrong. And that's what China tells its peoole, censoring heavily tbings like the Umbrella Revolution because shit will go down if people know that kind of protest could happen in "China".
My brother has lived in Hong Kong since before it was returned to China. Mainland China is slow to make changes in HK because they don't want a revolt. If you look up a few posts, Hong Kong was placed in the same list as Taiwan, Tibet, and the islands in the South Sea. Of these, Hong Kong officially belongs to China; the others are disputed. If you go to the Wikipedia article I referenced, there is a nice table of what's changed and what remained the same since 1 July 1997.