This is because Article 18 of the Basic Law of Hong Kong allows China to promulgate certain laws related to national security. Taiwan doesn't have this.

Sure. Regardless, legislative means were used, not force.

Legislative means we’re not used. China had no legal authority to do what they did... but no one will stop them.

You are correct to point out that force was not used (n/m the divisions of tanks that have been on the border), and Taiwan is different.

> Legislative means were not used. China had no legal authority to do what they did

You are in disagreement with the BBC on this point:

https://www.bbc.com/news/world-asia-china-52765838

> The Basic Law says Chinese laws can't be applied in Hong Kong unless they are listed in a section called Annex III - there are already a few listed there, mostly uncontroversial and around foreign policy. These laws can be introduced by decree - which means they bypass the city's parliament. Critics say the introduction of the law this way amounts to a breach of the "one country, two systems" principle, which is so important to Hong Kong - but clearly it is technically possible to do this.

It is a breach of the one country, two systems non-interference pact which the handoff was conditional on, therefore not legal.

The Central Government did have the authority under Article 18 of the basic law. Let's not kid ourselves here.