The legislation passed yesterday gives Beijing powers to shape life in Hong Kong as never before.

Residents were greeted by this in the harbor, the sign reads, Celebrates the national security law.

But many did not celebrate it, and police made their first arrests.

Under the new law, he's just some of the clashes between police and demonstrators.

Water cannons and tear gas were used to disperse the crowds.

So far, there have been more than 350 arrests, 10 of them related to the new law, which targets secession, subversion and terrorism with punishments of up to life in prison.

Well, here's an example of what constitutes an offence.

Hong Kong police tweeting Three females were arrested respectively, for showing materials with Hong Kong independence slogans in Causeway Bay, violating the national security law.

Anyone who organizes plans, commits or participates in committing secession or undermining national unification shall be guilty, often offense.

So that's three women arrested for holding banners with independents.

Slogans on that has scared pro democracy campaigners like Bonnie Young.

It is very vague.

So Ah, Hong Kong people can easily tracked into these ratlines accidentally with horrible, horrible consequences.

The maximum penalty as you sat is life imprisonment.

So is horrible for all of us.

Well, Andy, China's another pro democracy campaign who's previously cooled for Hong Kong independence.

This is what he said earlier today.

You just have to me, do I support from independents?

You're almost asking me to be in jail for over 10 years because we're not able to say independence.

Once I say that, I could be arrested well today as she marks 23 years since Hong Kong was handed back to China.

Ever since, people in the territory have enjoyed certain freedoms that do not exist in mainland China.

The agreement is widely known as one country, two systems on was supposed to last for 50 years, well, under the deal Hong Kong had to enact.

It's own at national security law, but that has never happened because of its unpopularity.

Then last year we saw these scenes over an extradition law.

Protests turned violent and turned into a broader anti China and pro democracy movement.

China doesn't want to see that happen again.

And so it stepped in.

While supporters off the law argue it will only affect a small number of people and is essential to restoring stability in the territory his Knicks alarm from a pro Beijing political party.

We need a lot to get back to normal.

We need a law to have a normal Hong Kong life back.

What is happening like before all this happens in home call, even though you're writing on them, tell you bump into someone will say, Oh my Oh my God, I'm sorry.

I'm sorry that I bump into you But we turn into this violence that Easton's last June and there's no way that we can stop this.

But it's not just Hong Kong residents who could face harsh penalties.

Article 38 of the law says it applies to offenses committed outside of Hong Kong by non residents, meaning if foreigners commit offenses overseas, they can be prosecuted when entering Hong Kong.

The US secretary of state, Mike Pompeo, has described it as an affront to all nations.

Here's Donald Clark from George Washington University, who spoke to Lucy on BBC World News earlier.

Well, you and I right now If in our conversation, if someone in Hong Kong, Hong Kong authorities decide that it violates the law undermines China's national sovereignty threatens China's national security, Then if either one of us goes to Hong Kong, um, you know, we're potentially liable to prosecution.

Gosh, that is worrying for many, many people, obviously not just journalists, students, scholars, everybody who has an opinion and would like to express it first, Professor Clark says This has implications for journalists, and we're already seeing an impact.

One freelance journalists in Hong Kong writes in Media, a Hong Kong news site and platform for independent independent writers and democracy advocates has taken down 100 plus articles at the request of its authors.

It's been a day of remarkable defiance, but a chill is also spreading through the city.

Well, let's get more international reaction.

His Mike Pompeo of US Secretary of state again free Hong Kong was one of the world's most stable, prosperous and dynamic cities.

Now, now we've just another communist run city where it's people will be subject to the party elites whims.

It's sad.

Indeed, this is already happening.

Security forces are already rounding up on Congress for daring to speak and think freely.

The rule of law has been eviscerated and, as always, the Chinese Communist Party fears it's own people more than anything else for Christopher Pass, in Hong Kong's final British governor before the 1997 handover, says China is a doubling down in their aggressive and loud ish behaviour, adding.

We really got work to do with allies not to start a Cold war, but to form a group of countries who will say If you behave in this appalling fashion China, we're going to call you out The British government says the law is a breach of the treaty between China and the U.

K, which gave Hong Kong its degree of independence, his UK Foreign Secretary Dominic Round.

It is a sad day for the people of Hong Kong on one which can only undermine international trust in the Chinese government's willingness to keep its word and live up to its promises.

And the prime minister, Boris Johnson, has sent a strong message by allowing up to three million people in Hong Kong who have British national overseas status because they were born before the Turkey returned to China to live and work in the UK for longer.

We made clear, Mr Speaker that if China continued on this path, we would introduce a new route for those with British national overseas status to enter the UK, granting them limited lead to remain with the ability to live on work in the UK and thereafter to apply for citizenship.

And that is precisely what we will do.

No well.

Our China correspondent Steve MacDonald says millions of Hong Kong citizens could end up moving to the UK after that announcement.

And he points out, the Chinese government has been publicly furious with UK for even threatening just such a move on one London not to proceed or risk unspecified retribution.

Now this has happened to a waiting for China's response.

Howard Zang is from the BBC Chinese service and he explained to me what that may look like the most direct potential retributions people can think of our diplomatic swell US economic measures.

The U.

K have been for the past few decades trying to enter the Chinese market on theirs.

The past few governments have been trying to court Chinese investment into the UK as well.

So many of these things can eventually be turned into bargaining chips or card being played.

So all those air possible and also in the past one.

It was during the government of David Cameron one.

The UK leadership met with the Dalai Lama and Tibetan exile leadership on there was a long term freeze off bilateral relations between the UK and Beijing and for quite a quite a while, until some type of road push mom happened later on on S 00 These past experiences could happen again in terms off any, perhaps changed, too.

Legal legislation in Hong Kong.

I mean, China is not one to move.

Once is made a position on that will probably be the case.

Will it not exactly at this very moment, more more honest?

And the scholars are pointing out This is becoming more of a political stand rather than introducing the law on many, even suggesting way, have to look at this at the bigger context of us.

China going head to head on Dinah's trying to pick a battleground.

Onda politically see thinking this is perhaps the best place we can pick a fight with the West with the US Andi, have a slightly better chance of winning on has Hong Kong's bean this sacrificial lamb at this moment?

How it just very quickly you have contacts, many of them in the territory.

Any idea how you can sum up the mood there?

At the moment, the mood are essentially on one side, people completely angry.

That's the anger side, but also fear turning this'll level of desperation.

Andi don't because most people lived in Hong Kong working Hong Kong.

No, It's a vibrant city where people he enjoyed most of freedoms and it's really economically vibrant.

And it's easy to do business and make money.

So people on one side love what they see.

And it used to be called the Pearl of the Orient on duh.

To see all of this almost evaporate overnight on Go to see the rule of law that they they got too used to almost now becoming a lot of a sudden the Samos mainland China.

And it's something people just still caught in happy disbelief on trying to figure out how to kind of move on from here.