Beijing made a decision to impose a national security law on Hong Kong after the city was paralyzed by historic and violent protests past year and several administrations failed to pass a local version of the legislation.
The Hong Kong government tried to introduce national security legislation in 2003, prompting massive protests and the withdrawal of the bill. China's National People's Congress (NPC) announced the measures following pro-democracy protests in the semi-autonomous territory.
Hong Kong's Beijing-appointed leader, Chief Executive Carrie Lam, attempted to reassure the global community on Friday night that the city would remain a "very free society, where freedom of expression, freedom of protest, freedom of journalism, will stay".
"Legislating on Hong Kong's behalf without the direct participation of its people and legislature would challenge that principle", the foreign minister said.
Now, after a wave of sustained and often violent protests in Hong Kong a year ago, Beijing is attempting to push the law through.
"Can businessmen tell Hong Kong people, why are there more USA companies, US businessmen and USA investments in mainland China than Hong Kong?" he wrote in a Facebook post. We're going to crack down.
One protestor, Eddie Chu, was removed by security.
Communist Party rulers in Beijing on Friday unveiled details of the legislation that critics see as a turning point for the former British colony, which enjoys many freedoms, including an independent legal system and right to protest, not allowed on the mainland.
What's more, Professor Chan says the proposed law will contravene Article 23. China can place them into Annex III of the Basic Law, which covers national laws that must then be implemented in Hong Kong - either by legislation, or decree. He warned that the pro-democracy opposition should not "underestimate the determination of the Chinese government to deal with the issues of Hong Kong".
"There is a growing list of disagreements (Hong Kong being but the most recent) but no strategic rationale for the relationship or plan to limit friction".
According to the BBC, the new law would criminalize separatism, as well as the subversion and undermining of the authority of the Communist Party.
Hong Kong's China-backed Chief Executive Carrie Lam said the city would fully cooperate with China to enact the legislation.
China's army already has a garrison in Hong Kong but soldiers have not intervened in the protests, though the city's mini-constitution, the Basic Law, authorises local officials to request military help to protect public order.
US Secretary of State Mike Pompeo labelled the proposal as "disastrous".
If there were sanctions associated with any national laws to be included in the annex, Professor Chan says it should go through Hong Kong's parliament because the judicial systems are so different. Hong Kong's "one country, two systems" constitutional arrangement means that China's national laws do not apply to the city. Days later, Hong Kong police arrested 15 high-profile democracy activists including 81-year-old Martin Lee - often called the city's "Father of Democracy" - on charges related to participating in illegal rallies.
"I was very upset when I held the newspaper with the headline that the national security law has arrived in Hong Kong", said a newspaper vendor named Man, who declined to give her full name, Reuters reported.