Explainer: inside Hong Kong's divisive new law

Hong Kong is held up as China’s freest and most cosmopolitan city.

And it's being pushed onto a more authoritarian path.

The city is undergoing its biggest change since returning to Chinese rule in 1997 - due to new legislation, introduced by Beijing in the name of national security.

Permanent and non-permanent residents of Hong Kong can now be imprisoned for up to life for crimes of secession, subversion, terrorism and collusion with foreign forces.

Take the peaceful Occupy protests of 2014: that could now earn demonstrators 10 years in jail, if foreign links were proven.

[Amnesty International’s Joshua Rosenzweig, saying:] "The definition of the crimes, separatism, subversion, terrorism, collusion with foreign forces to endanger national security, all of these things are still, in our view, open to abuse by the authorities, and could possibly be used to punish people for things that should be protected activities, particularly things related to freedom of expression, freedom of peaceful assembly, that type of thing."

To enforce the measures a new security agency has been set up, which isn’t under the jurisdiction of the local government.

It will be the first official presence of mainland security and intelligence agents in Hong Kong, whose powers will go beyond local laws.

[Amnesty International’s Joshua Rosenzweig, saying:] "We're quite worried about what this law means in terms of the, not only the scope to which law enforcement may further restrict people's rights in Hong Kong, but also the powers that this law gives to the authorities, both the Hong Kong authorities and central government authorities."

Until now, Hong Kong has boasted an independent judiciary and separate legal system based on common law - hailed as the key to its success as a global financial hub.

The new law allows Hong Kong’s leader to appoint judges for national security cases.

It also allows for serious and complex cases to go to mainland courts.

[Pan-Democrat Legislator Dennis Kwok, saying:] “... unfortunately, this is not common law-based. This is not what we understand to be the normal legal principles applying to situations that we are normally familiar with."

The contents of the law were kept secret until it took effect - even from Hong Kong’s leader Carrie Lam.

[Hong Kong Chief Executive Carrie Lam, saying] "... we have not seen the complete details of the proposed legislation.”

Now it’s in effect, assessments suggest it’s stronger than many had feared - both in scope and penalties.

The reach of the law has stunned some legal scholars.

And condemnation from the international community has been swift.

[European Council President Charles Michel, saying]: ''We deplore this decision."

But it’s cause for celebration for pro-Beijing supporters.

Officials say the law is vital for national security and it will plug holes in the city’s defences.

They say only a small number of people will be affected - and broader rights and freedoms will not be eroded.

But a chilling effect is underway.

Arrests have already been made, mere hours after the law was enacted.

Prominent activists have disbanded their groups, and said they expect to be among the first to be targeted.

[Activist Joshua Wong, saying:] "I will probably be the prime target of the new law. But what makes me fear is not my potential imprisonment, but the gloomy fact that the new law will be a threat over the city's future and not only my personal life.”