Beijing CNN  — 

A law professor at a prestigious Chinese university in Beijing has been suspended and put under investigation for writing a rare essay critical of President Xi Jinping.

Professor Xu Zhangrun of Tsinghua University was told last weekend he was being removed from all teaching positions until the investigation into him was complete, his colleague and friend Guo Yuhua told CNN Wednesday.

Guo, a sociology professor at the same university, said Xu’s work as a teacher, researcher and tutor had been suspended. She said the details of Xu’s suspension were still unclear but it had been in a major part due to an essay he published in July 2018.

The lengthy article, titled “Imminent Fears, Immediate Hopes,” challenged the direction of China under Xi and called for the reintroduction of presidential term limits, which were controversially removed by the government in early 2018.

“Suddenly, as if out of nowhere, we had a ‘supreme leader’ with no checks on his power; how could people not have all kinds of strange imaginings and new fears?” Xu asked in his essay.

The investigation into Xu is just the latest action taken by the Chinese government to repress dissenting voices or opinions that run contrary to the ruling Communist Party’s policies.

It also shows no voices challenging Xi will be tolerated as he continues to consolidate his position as China’s most powerful ruler since Chairman Mao Zedong.

Speaking to the New York Times by text earlier in the week, Xu said he didn’t know what would happen to him next.

“I’ve been mentally preparing for this for a long time. At the worst, I could end up in prison,” he told the newspaper.

Fellow teacher Guo said it wasn’t clear why authorities had waited so long to take action after the essay was published. She said if one person was banned from speaking, it was a problem for everyone.

“As for myself, I speak not because I’m brave, it’s because I’m frightened. And I’m worried this may happen to anyone else,” she said.

Freedom of speech?

The move is especially shocking given the prestigious reputation of Tsinghua University, which is over 100 years old and has been consistently rated as one of the world’s best schools.

The most recent Times Higher Education World University Rankings placed Tsinghua as the top institution in Asia and 22nd overall.

The report attributed Tsinghua’s high global ranking to “improvements to its teaching environment, in particular increases in institutional income and the share of PhD degrees awarded.”

Beijing’s equally famous Peking University, ranked 31 on the same Times report, has also been subject to a crackdown in the past few months, targeting the school’s Marxist student leaders who had been working to promote workers’ rights across China.

A number of Peking University student activists have been taken into custody by authorities since August, some of whom haven’t been seen since.

Presciently, Xu criticized the repression and intolerance for academics under Xi’s increasingly oppressive regime in his essay, saying it would hamper free discussion among Chinese intellectuals.

“In an atmosphere such as this, how can there be any freedom of speech? Without intellectual freedom and the independent spirit, what hope is there for people to explore the unknown, for the advancement of scholarship or for intellectual creativity,” he said.

Tsinghua University did not respond to CNN’s requests for comment.