It thus establishes the legal system and enforcement mechanisms for the HKSAR to safeguard national security.
Al Jazeera's Katrina Yu, reporting from Beijing, noted the passage of the law had been fast-tracked.
"It will only target an extremely small minority of people who have breached the law, while the life and property, basic rights and freedoms of the overwhelming majority of Hong Kong residents will be protected", Hong Kong leader Carrie Lam said.
China said it would retaliate.
The legislation was unanimously approved by China's rubber-stamp parliament on Tuesday morning, little more than six weeks after it was first unveiled, sending shockwaves through semi-autonomous Hong Kong and beyond. Its chief executive will most likely have the right to appoint judges for the hearings of the national security cases. "I think that's quite obvious", Ng said.
But the latest "Mechanisms for the Preservation of National Security" as the law is called officially, allow "the organs of the Central People's Government for the protection of national security to set up institutions in the Hong Kong Special Administrative Region, " a clause which, critics say, spells the end of Hong Kong's relative autonomy.
Wong, 23, said on his Facebook page that for democracy activists, it is "no longer a joke to fear for one's life", adding that they also face jail terms, interrogations in special detention centers and being sent to China for trials. China's state media have repeatedly accused Wong as well as other prominent pro-democracy figures such as Jimmy Lai and Martin Lee of "collusion with foreign powers" for their engagements with USA and other foreign governments.
In addition to the lack of transparency surrounding the security law's legislative process, Beijing's choice of timing to impose the law has raised eyebrows.
China's parliament passed national security legislation for Hong Kong on Tuesday, setting the stage for the most radical changes to the former British colony's way of life since it returned to Chinese rule nearly exactly 23 years ago.
"Beijing can't prevent millions of people from voting, but they can remove candidates by disqualifying them", the barrister explained.
Authorities can surveil and wiretap persons suspected of endangering national security.
The contents of the law have so far been kept secret from Hong Kong's 7.5 million inhabitants, sparking alarm, anger and fear.
"We can no longer distinguish between the export of controlled items to Hong Kong or to mainland China", Pompeo said in a statement. But at the same time, Ho also hopes Hong Kongers won't "lose liberty and face the possibility of going to jail". Instead the news filtered out via pro-Beijing politicians and local media outlets in Hong Kong.
It is unclear if attending the unauthorized rally would constitute a national security crime if the law came into force by then.
Wen Wei Po and Ta Kung Pao - two Hong Kong newspapers that serve as conduits for Beijing's official policy - also confirmed the passing of the law, as did multiple local Hong Kong media outlets citing anonymous sources in Beijing. Arguing that the security laws will diminish the city's autonomy, the Trump administration is moving to treat Hong Kong equally with mainland China for trading purposes.
"Their aim is to govern Hong Kong through fear from this point forward", Rosenzweig said.
", I had no choice but to make a heavy-hearted decision to disband our Hong Kong members and operations", Chung said in a Facebook post after the law passed. "We went out on the streets at lunchtime to speak to ordinary people at lunchtime to try and gauge their opinions and none of them wanted to comment - that's very unusual here in Hong Kong", he said.