Article 23 was unanimously passed by the city’s pro-Beijing parliament, which targeted a range of treasonous offenses.

Officials say the law is essential for the city’s stability, but opponents called the law a “nail in the city’s coffin.”

China has long pushed for the creation of the law and stated that “smears” by critics would fail.

The new law allows for closed-door trials, gives the police the right to detain suspects for 16 days without charge, and penalties including life sentences along with other things.

“The new national security legislation is going to double down the repression of freedoms in Hong Kong with extended egregious sentences and a broadened definition of national security,” said Frances Hui, an activist now based in the US, who described the legislation as a “final nail in a closed coffin.”

A group of over 81 law-makers and public figures from across the world issued a joint statement on Tuesday expressing “grave concerns” over the legislation, which expands on the National Security Law imposed by Beijing in 2020. the legislation also criminalizes secession, subversion, terrorism, and collusion with foreign forces.

“The legislation undermines due process and fair trial rights and violates Hong Kong’s obligations under international human rights law, jeopardizing Hong Kong’s role as an open international city,” the statement said, calling it yet another “devastating blow” to freedom.

The US said that it was “alarmed” by the “sweeping and… vaguely defined” provisions in the legislation, a concern shared with the EU, which said that the law could affect the city’s status as a business center. Meanwhile, the UK’s Foreign Secretary David Cameron said the law would “further damage rights and freedoms” and “entrench a culture of censorship” in the former British colony. Hong Kongers have already told BBC that they are already being careful with what they say around their friends and colleagues, fearing an “informant culture” has developed in the city.

Lord Cameron’s comments sparked a strong response from the Chinese Embassy in the UK, which criticized his remarks as “a serious distortion of facts.” China’s government has also responded to the criticisms of Article 23, stating it is “unswervingly determined to safeguard national sovereignty, security and development interests, implement the ‘one country, two systems’ policy, and oppose any external interference in Hong Kong affairs.” “All attacks and smears will never succeed and are doomed to fail,” foreign ministry spokesman Lin Jian told a regular press conference in Beijing.

Hong Kong’s leader, John Lee, has defended the legislation-which was fast-tracked through its final phase on Tuesday-saying that the legislation would help the city “effectively prevent, suppress and punish espionage activities, conspiracies and traps from foreign intelligence agencies, and infiltration and sabotage by hostile forces.” “From now on, the people of Hong Kong will no longer experience these harms and sorrows,” he added.

But those who led the pro-democracy protests against China’s increasing influence on the city see the new law as a loss to yet another battle.

It brings Hong Kong” one step closer to the system of mainland China”, former Hong Kong lawmaker Nathan Law, who is now in exile in the UK, told BBC. “The chilling effect… and the result of a collapse of civil society is impacting most Hong Kong people.”

Ms. Hui, who is now the Policy and Advocacy Coordinator at the Committee for Freedom in Hong Kong Foundation, said she is also concerned that the laws can be used to target Hong Kongers living overseas or their families and friends back home. The city has previously offered rewards for information on activists who had fled overseas, and arrested four people in Hong Kong who “endanger national security.” Ms. Hui left Hong Kong in 2020 after Beijing imposed the NSL which has seen more than 260 people arrested. It was introduced as a response to massive pro-democracy protests which engulfed the city in 2019. She said civil liberties are “long gone’ in Hong Kong four years after the NSL had taken effect.

Chris Pattern, Hong Kong’s last British governor, described the legislation as  “another large nail in the coffin of human rights and the rule of law in Hong Kong and a further disgraceful breach of the Joint Declaration.”

Hong Kong was handed back to China from the UK in 1997 under the policy of “one country, two systems,” which guaranteed the city some degree of autonomy. While Beijing and Hong Kong still insist that they have followed this policy, international critics have said that China’s grip on the city has only tightened with time.