China has imposed a sweeping national security law on Hong Kong, dramatically tightening its grip on the semi-autonomous city in a historic move decried by Western nations as a threat to the financial hub's freedoms.
China has taken matters into its own hands after last year's tumultuous anti-government protests in semi-autonomous Hong Kong city that often descended into tear gas-filled clashes, arrests, and property damages.
On Tuesday, Beijing imposed a new security law on Hong Kong that outlaws subversion, secession, terrorism, and colluding with foreign forces to undermine national security.
On Wednesday, a man found in possession of a Hong Kong independence flag became the first person to be arrested under the law for the city.
China's law has raised questions about the future of the semi-autonomous territory but here is what we do know:
What's in the new law?
The new law gives Beijing jurisdiction over "very serious" national security crimes, with offenders facing up to life in prison.
The law also empowers China to set up a national security agency in the city with staffers from mainland China.
China security agencies will also be able to operate publicly in the city for the first time, unbound by local laws as they carry out their duties.
The new suite of powers radically restructures the relationship between Beijing and Hong Kong, toppling the legal firewall that has existed between the city's independent judiciary and the mainland's courts.
The new law was passed in just six weeks, skipping Hong Kong's fractious legislature and the precise wording was kept secret until it came into effect late Tuesday.
According to BBC, "only a handful of people had seen the full text of the law before it was enacted. They did not include the territory's Chief Executive, Carrie Lam".
What is Hong Kong's special status?
In the run-up to Britain returning Hong Kong to China in 1997, a "one country, two systems" deal was forged to allow the city to maintain certain freedoms and autonomy for 50 years.
Those liberties included a free market economy, an independent judiciary, free speech, and a local legislature.
As a result many countries, including the US, brought in laws that allowed them to treat Hong Kong as a separate trade entity to mainland China.
The arrangement turned Hong Kong into a world-class financial centre on a par with London and New York.
What does China want?
For several years now, Chinese officials have increasingly expressed frustration and anger at what they perceive as a weak national security regime in Hong Kong, the freewheeling financial hub which has a high degree of autonomy.
The large and sometimes violent anti-government protests that erupted last year have sharpened that frustration, with China's Communist Party leadership, determined to thwart what it describes as threats of terrorism, independence, and subversion.
China's most senior official in Hong Kong, Luo Huining, warned in April that the city must urgently introduce national security law.
"If the ant-hill eroding the rule of law is not cleared, the dam of national security will be destroyed and the wellbeing of all Hong Kong residents will be damaged," he had said.
How can China do it?
Under the delicate "one country, two systems" formula, China agreed to protect Hong Kong's extensive freedoms, autonomy, and independent legal system.
Those freedoms are protected by the Basic Law, a mini-constitution that guides the relationship between Hong Kong and Beijing.
But Article 23 of the document also states that Hong Kong must "on its own" enact laws against treason, secession, sedition, subversion, and the theft of state secrets. It also seeks to outlaw ties between local and foreign political groups.
The Hong Kong government proposed local legislation in 2003 but met vast opposition before it could be passed into law, with more than 500,000 people marching peacefully against it.
Local officials acknowledge their obligations but some, including leader Lam, said recently that the time is still not right.
However, the Basic Law also gives Beijing the power to annex national laws into the document – which the local government must then legislate for or effectively impose on the city by executive fiat.
Local lawyers and politicians sometimes call this the "nuclear option" but some scholars have questioned whether this power of promulgation applies to Article 23.
How has it been received?
Activists in Hong Kong say the law will undermine civil liberties and might be used to suppress political activity.
Many fear that new national security legislation would prove a "dead hand" on the city's large and pugnacious press and rich artistic traditions while curbing its broad political debates.
The law and the way it was enacted prompted the US in May to announce that Washington will no longer treat Hong Kong as autonomous from Beijing, meaning that Hong Kong no longer qualifies for its special status under US law.
That statement unnerved investors worried about the risk to the Chinese-ruled city's status as a global financial hub.
Twenty-seven countries, including Britain, France, Germany, and Japan, have urged Beijing to "reconsider the imposition" of the legislation, saying in a statement to the UN Human Rights Council that it "undermines" the city's freedoms.
US has threatened new countermeasures.
But Lam, a pro-Beijing appointee, has rejected concerns the law will end Hong Kong's freedoms.
How will this pan out?
The protests in Hong Kong and the reaction in Beijing illustrate a fundamental divide that has once again bubbled to the surface.
The freedom of expression and other rights that Hong Kong residents have under "one country, two systems" allow for protests and public criticism of the government. It can, at times, be messy.
China's ruling Communist Party sees stability as vital to maintaining its grip on the country, including the territories of Hong Kong and nearby Macao.
"One country, two systems" is not about to disappear.
Hong Kong will continue to manage most of its local affairs, from taxation to common crime.
But Beijing is poised to wield an increasingly heavier hand when it comes to dissent and any possible challenges to its ultimate control of Hong Kong.