GÖTTINGEN , Germany — When the tanks rolled into Tiananmen Square in Beijing on June 4, 1989, many Hong Kongers watched in horror on their TVs. A few days before, one million of them had marched in solidarity with the rebellious Chinese gathered in the square to ask for more liberalism and democracy from the Chinese authorities. Thirty years on, it is Hong Kong that is fighting for democratic values — for its very political survival, actually — against another onslaught by the same Communist government in Beijing.

The situation is dire. The Hong Kong government, now apparently under the direct influence of Beijing, has proposed amending existing extradition laws to give unprecedented power to Hong Kong’s leader — an official essentially chosen by the Chinese Communist Party (C.C.P.) — to arrest people in Hong Kong and send them to China to face trial. The new bill would apply to anyone — a Hong Kong citizen, a mainlander, even foreigners traveling through the city — accused by the Chinese authorities of having broken Chinese law.

The Chinese legal system is famously corrupt and, too often, a tool of repression. The new extradition law could be used to squelch any form of political opposition or dissent. Chris Patten, the last British governor of Hong Kong, has called it “the worst thing” to happen to the city since Britain handed control over it to China in 1997. When the legislation passes — which now seems near certain, and imminent — it will spell the death of Hong Kong as the world has known it.

In 2014, at age 21, I was one of the tens of thousands of protesters in Hong Kong’s pro-democracy Umbrella Movement. We demanded that genuinely free elections be held in the city, as set out in its Basic Law. Yet the government ordered liberal use of tear gas against us; some protesters were severely beaten in dark street corners. One could say that after more than two months of sit-ins, the Umbrella Movement failed: None of our demands were met.