The sudden arrest of Sadegh Zibakalam, a vocal Iranian academic, may signal to other tolerated critics that they too, even if they haven't advocated for regime change, might now face the threat of arrest.

Iranian media widely reported that Zibakalam, a former professor of political science at Tehran University, was arrested on Sunday by security forces while en route to the Tehran International Book Fair to unveil his new book, titled "Why Don’t They Arrest You and What Will Happen Afterwards?".

In a tweet after the news of Zibakalam’s arrest broke, Mehdi Keshtdar, managing director of the state’s judiciary news agency Mizan, denied the reports that he had been arrested on the street.

The judiciary insists that the 66-year-old academic was “summoned” to serve multiple sentences totaling three years for “propaganda against the state” as well as “spreading falsehood” on social media to affect the public’s opinion.

Zibakalam is known for speaking to foreign media on controversial matters.

His 18-month prison sentence for “propaganda against the state” by the Revolutionary Court in 2018 was for an interview with Germany’s Deutsche Welle which the court said was a "counter-revolutionary and hostile website."

In the interview, Zibakalam commented on the "disappointment of anti-government protesters with the entire regime apparatus" and said 70% of Iranians would say no to the Islamic Republic if there were a referendum to decide the type of government in Iran.

The title of his book alludes to allegations suggesting that, unlike other 'reformist' critics like former official Mostafa Tajzadeh, Zibakalam has been "immune" to arrest despite making controversial remarks over the past decade. These include his criticism of the country's nuclear policies and its anti-Israel rhetoric.

This immunity was believed to be due to Zibakalam never advocating for the overthrow of the Islamic Republic.

“Who says we should destroy Israel?” Zibakalam who openly voiced his recognition of the State of Israel asked in an interview with historian and filmmaker Hossein Dehbashi in 2014. “It’s no joke when you write ‘Israel must be destroyed’ on your missiles’,” he said.

Zibakalam refusing to step on American and Israeli flags in 2021

“Israel has never said it wants to destroy us ... Even Palestinians recognize Israel. We are more catholic than the pope,” Zibakalam, who is supportive of the right of the Palestinians to have their own state, said in a debate in 2015.

In April last year he said “annihilation of Israel and fighting America” were not among the goals of the Islamic Revolution of 1979 and these slogans were often used by authorities to justify their failures.

In January, Zibakalam came under massive attacks from hardliners after he said Israel “does not kill innocent people” in an interview.

Many dissidents argue that not being arrested after such bold criticism is evidence that Zibakalam is “the regime’s safety valve” and his activities serve the authorities’ wish to show that freedom of expression exists in the Islamic Republic.

“Good! Zibakalam is NOT opposing the mullah regime in Iran but [is] in fact a willful propaganda stooge & proud Jew-hater. The regime parades him out in front of TV cameras often to claim they allow ‘criticism’ of their policies. He's a regime loyalist & a FRAUD!,” California-based Iran commentator Karmel Melamed tweeted after Zibakalam’s arrest.

Others, including some of his critics, have risen to his defense in principle.

"Now that he has fallen from grace, I have always been opposed to #SadeghZibakalam, from explicit criticisms in class to heated debates face-to-face at conferences, and later by denying and rejecting his positions and track record in public. But today, I definitely say that his arrest is unacceptable, and he should be released,” Tirdad Bonakdar, a member of the Central Committee of the banned National Front, founded by nationalist Mohammad Mosaddegh in 1949, wrote on X.

Recently, Zibakalam said in a tweet that the security outfit at Allameh Tabataba'i University had not allowed him to enter the campus to participate in a debate to which he was invited by the hardliner Students Basij militia.

Within a day of his arrest this weekend, Zibakalam’s book became unavailable on Tehran's Digikala online shop – an Iranian e-commerce company. It’s unclear whether the book sold out or if the retailer was instructed to remove it from its online platform.