This means all of its residents, including the 100,000 Australians who live there, will be at the mercy of an opaque legal system which is not accountable to anyone except the Chinese Communist Party.
While day-to-day life for many ordinary people will not change, the risks they face going about their business will be on par with those who live in mainland China. This means foreign companies and executives can unwittingly fall foul of the Chinese authorities if they are considered to be a threat to national security.
The Australian business community in Hong Kong does not want to talk about these risks publicly because they know what happens to companies who comment on China. A survey by the American Chamber of Commerce in Hong Kong, however, found that 30 per cent of its members planned to move capital, assets or operations out of the city.
While big business says it remains confident of the city's future, Australians working in the media, data management or non-government organisations are particularly nervous.
"It will be essentially little different than having your data stored on the mainland," says Wilson Leung, a Hong Kong barrister and member of the Progressive Lawyers Group.
"When the law is passed you will have mainland security agents in Hong Kong who will be able to exert draconian measures such as searches. They can come in, take your data centre and use it against you."
However, the implications of the new laws are far wider than data security. Many of the young protesters who rallied in the streets last year say they are deleting their social media accounts and records of online conversations out of fear they will be extradited to a mainland China's "black jails".
Leung and other lawyers say offenders, ranging from the most prominent pro-democracy activists to a 14-year-old student caught up in a protest march, could be detained. It is unclear for how long, although local media reports speculate that the period could be five to 10 years. TheSouth China Morning Postquoted sources on Monday saying the detentions could be indefinite.
While the details have still not been released, China will be able to set up Hong Kong security operation which has been compared to a secret police force. The Beijing-appointed Hong Kong chief executive will have the power to appoint judges and China's security law takes priority if conflicts with Hong Kong's.
"It is basically transplanting the mainland legal system onto the Hong Kong legal system," says Leung. "There is a real possibility you could be arrested and detained by mainland agents in Hong Kong and sent over the border for trial in the mainland legal system. It is a turbo-charged version of the extradition bill."
A proposed bill which would have allowed criminals in Hong Kong to be extradited to mainland China triggered last year's mass protests. It was later shelved, but the fallout of that period is far worse for many Hong Kong residents than the extradition bill would have been.
There is unlikely to be a repeat of those mass protests on July 1, when a march is usually held to mark the 1997 handover, although local media said 4000 police would be deployed in case there was any unrest.
Lawyers like Leung say it is not just Hong Kong residents at risk. Expatriates would also need to be on their toes. It is unclear what will happen if someone working for Macquarie Bank or ANZ participates in a protest or posts critical comments on social media - or if an economist writes an unfavourable report about China's debt levels.
However, Leung warns: "They should be very worried. We have seen on the mainland that foreign individuals and companies may easily fall foul of these vague national security concepts."
China this month charged two Canadians with espionage. Former diplomat Michael Kovrig and businessman Michael Spavor are alleged to have spied on national secrets. Their detention is widely seen as retaliation for the arrest of a senior Huawei executive in Vancouver.
Beijing is clearly in a rush to get this across the line while the rest of the world is distracted by coronavirus. It took the rare step of holding two meetings of the Standing Committee of the National People's Congress, the body drawing up the legislation, within two months. The NPC was expected to pass the law on Monday.
Hong Kong's leaders and pro-Beijing politicians have spent the last two weeks vigorously defending the security laws, which they say will continue to protect its citizens' human rights.
However, they do not really know what they are promoting as none of them has been allowed to see a full draft of the bill.
One thing everyone agrees on is that China's emboldened approach to Hong Kong has a good chance of stamping out the protests. This is good news for city's bankers and other executives keen to see an economic recovery without the distraction of tear gas in the streets of Central at lunchtime.
But for the tens of thousands of young protesters who spent most of their weekends on the streets last year, this is the final nail in the coffin for their city of birth.