“Recent developments in China have delivered a big wake-up call to Chinese liberals that nothing will come easily,” he said.

Image Mr. He in 1982, when he was finishing his law studies in the city of Chongqing. “It was an optimistic era,” he said. “There was a feeling that Chinese society was slowly thawing.”

Even while banished from the Chinese news media, Mr. He commands a warm following among students and lawyers. He is still allowed to teach foreign legal history and comparative law at Peking University, which he said is more tolerant of mavericks than many other Chinese campuses.

While he was being interviewed for this article, a student waited patiently to shake his hand. During another interview, editors at a law publisher greeted him as an old friend.

“He’s a public intellectual and has a big following, but of course it’s suppressed now,” said Eva Pils, a law scholar at King’s College London who studies Chinese human rights lawyers and has known Mr. He for about 15 years. “But I think he sees himself in a longer historical trajectory as one of those Chinese scholars who spoke up whatever the consequences.”

China’s tradition of liberal dissent burst out of hiding in the late 1970s, when the nation was recovering from the upheavals of Mao Zedong’s final years. For Mr. He, the scars from that time were deeply felt.

He was born in Shandong Province in eastern China, where his father, He Chuanyou, was a doctor who had once worked in the military. But the father was engulfed in the mass persecutions of the Cultural Revolution, and in 1970 he killed himself by severing the arteries in his legs, Professor He said.

These memories swelled 10 years ago, when Bo Xilai, an ambitious politician, began reviving Mao-era songs and rhetoric in Chongqing, a city in southwest China. Mr. He issued an open letter in 2011 denouncing Mr. Bo’s red revivalism, and he was jubilant when Mr. Bo fell in a scandal the following year. But dangerous nostalgia for Mao’s time persisted, Mr. He said.