Hong Kongers are back in the streets. As the South China Morning Post notes, protesting is in the semi-independent city-state’s “DNA”: Smaller demonstrations are nearly constant, and massive ones like this one—usually mounted to protect the city’s hard-won political independence—happen every few years. Still, the scale of the current outcry is unusual, with hundreds of thousands protesting a new extradition law on Sunday in what may have been the largest marches since the city’s handover to Chinese rule.

On Monday, as riot police clashed with a small group of several hundred protesters outside Hong Kong’s legislature—Sunday’s much larger protests were mostly peaceful—Chief Executive Carrie Lam vowed to press on with the bill. It will be up for debate on Wednesday, and with pro-Beijing lawmakers enjoying a majority in the legislature, it is very likely to pass into law.

Under the proposed law, Hong Kong’s chief executive would have the authority, on a case-by-case basis, to order the extradition of criminal suspects to countries not covered by its current extradition treaties—including mainland China.

The former British colony has been part of China since 1997, but it maintains autonomy under the “one country, two systems” arrangement. This status has allowed Hong Kong to become a major global financial hub and maintain a degree of political freedom unknown elsewhere in China, including an elected legislature and a free and rambunctious media.

But as China’s political and economic clout has grown, so has the pressure on Hong Kong. The city’s special status is due to end in 2047, by prior arrangement, but leaders in Beijing don’t seem to want to wait that long, creating several flashpoints in recent years. In 2012, Hong Kongers took to the streets to protest a new school curriculum that included a “patriotic education” requirement. In 2014, the Occupy Central movement, also known as the Umbrella Revolution, shut down the city’s financial center in response to a new election law that allows a Beijing-approved election committee to prescreen political candidates for the city’s chief executive office.

Proponents of the new extradition law, including Lam, say it will only be used in specific cases and have pointed to a recent gruesome case of a Hong Kong man accused of murdering his pregnant girlfriend in Taiwan, who can’t be sent to face trial there because Taiwan is also not currently covered by an extradition treaty. Supporters also argue that Hong Kongers could still challenge extraditions in court, that no one at risk of torture or the death penalty would be extradited, and that suspects would only be extradited for offenses that are also illegal in Hong Kong. The government also removed nine financial crimes from eligibility for extradition following backlash from the business community.

But pro-democracy activists in Hong Kong fear the law will be used to further infringe on Hong Kong’s status as a haven for critics of Beijing’s policies. A few recent incidents suggest these fears are not overblown. In 2015, five people associated with a controversial Hong Kong bookstore known to sell materials critical of China’s central government went missing and eventually turned up in mainland custody. Beijing has also recently become bolder about detaining foreign nationals on political grounds. In December, the government arrested and charged two Canadians with espionage: Michael Kovrig, a former diplomat who worked in Beijing for the International Crisis Group, and Michael Spavor, a consultant who worked on the China–North Korea border. Their arrests came shortly after Canada’s detention of Huawei executive Meng Wanzhou on a U.S. warrant and are widely seen as retaliatory.

Because of its more permissive political climate, Hong Kong is used as a base of operations for many nongovernmental organizations and journalists—both local and foreign—whose work would not be possible in the mainland. In theory, the extradition law is written in such a way that those workers would be protected from being sent to China on political charges, but with a fairly compliant Hong Kong government, it’s not hard to imagine those in power in the city concocting a pretext to allow China to arrest someone it sees as critical or otherwise threatening in Hong Kong territory.

For its part, the mainland Chinese government has barely acknowledged the protests and has censored any mention of them in Chinese media. The state-run, English-language Global Times, which is aimed at an international audience, wrote in an editorial that the law is meant to prevent Hong Kong from becoming a “heaven for criminals” and accused foreign governments of stirring up the protests, noting that both House Speaker Nancy Pelosi and Secretary of State Mike Pompeo have expressed concern about the law.

The protests come a week after the 30th anniversary of the Tiananmen Square massacre, an event that is marked with a candlelight vigil every year in Hong Kong but is barely remembered, much less observed, in mainland China. (This year, many activists expressed fears that the 2019 vigil could be one of the last.)

China’s leaders often justify authoritarianism on cultural grounds, arguing that those who press for more democracy and civil liberties are attempting to impose Western values and political ideas on a place and a culture where they’re not suited. Hong Kong (along with Taiwan, which is also under increasing pressure from China) represents a refutation of that idea, as does the fact that young Hong Kongers are more critical of Beijing than their parents, despite China’s increasing prosperity and cultural influence. Hong Kong’s citizens are likely to continue to push back, and more flashpoints can be expected, but the city-state may not be able to resist the pressure from the superpower next door for much longer.