On Sept. 17, Yang Hui was summoned from his afternoon math class by his junior high school’s vice-principal, according to an account the student provided to the state-owned Beijing News newspaper that was published on Tuesday. The 16-year-old quickly learned that he was in serious trouble. Three plainclothes and a uniformed police officer were waiting in the principal’s office. They asked for his phone, interrogated him, conveyed him to the police station for further questioning and then locked him up in a local detention center. His apparent crime?

He was re-tweeted.

This is a novel transgression. Two and half weeks ago, officials announced new regulations meant to rein in the allegedly rampant rumormongering that the government claims disrupts the harmonious development of China’s Internet. Few here believe that the new rules are much more than the latest, and most heavy-handed, attempt to check online dissent and re-assert government control over how China thinks, talks and tweets about its leaders. The terms stipulate that anyone whose message is re-tweeted more than 500 times on Chinese microblogs or is seen by more than 5,000 online users can be subject to jail for up to three years if the original post turns out not to be true. As tools of repression go, this is a powerful one, and Yang’s experience -- and the public outcry that followed it -- highlight its strengths and limitations.

Yang’s adventure began Sept. 12 in Zhangjiachuan, a remote county in Gansu province. That evening, a man’s body was found below a karaoke club. (In China, such locales are strongly associated with prostitution and organized crime and are often believed to operate with the tolerance, if not support, of local governments.) The local government claimed that the man had committed suicide by jumping from the club’s upper floors (a suspicious story, considering the karaoke club was housed in a two-story building, according to the Los Angeles Times). In the interview with the Beijing News, Yang said that he heard from witnesses that the man had died after being beaten by police.

Five years ago, Yang might have simply kept such mumblings to himself. But the young man came of age with microblogs, and two days after the death in front of the karaoke club he sent out the first of his now deleted (almost certainly censored) posts on China’s QQ and Sina Weibo microblogging services. The messages called into question the government’s account of the death, claimed that the owner of the karaoke was a local court official (apparently that wasn’t true and the karaoke club belongs to the wife of another official) and made an impassioned call for protest (there was a gathering, though it’s not clear whether it was initiated by Yang’s appeal).

“It’s been three days and two nights since the 9.12 Zhangjiachuan murder and still the police don’t act, the media don’t report, and the people don’t know the truth,” one of the QQ tweets said, according to the state-run but highly independent Southern Metropolis Daily. “He who died can rest in peace, we will seek justice for you!”

As of Sept. 20, that post had been re-tweeted 962 times, according to the Southern Metropolis Daily.

Sometime during this sequence of events -- itself blurred by conflicting interpretations and deleted online activities -- Yang’s conduct put him at odds with the anti-rumormongering law, at least in the eyes of the Zhongjiachuan government. And so began the trip to the principal’s office and what looked to be a one-way ticket to administrative detention -- the murky system that allows police to lock up low-level offenders for up to 15 days without judicial review.

The local authorities may have believed that their actions wouldn’t draw much attention. They were wrong. Almost from the moment of Yang’s arrest, the news spread online, sparking outrage so great that by Sunday night it largely overshadowed discussion of the life sentence given to ousted Politburo member Bo Xilai that morning (discussion of that verdict was heavily censored on microblogs).

Much of the anger was directed at the anti-rumormongering law and the perceived bullying of a 16-year-old. The uproar became so intense that some search terms associated with the case -- including “administrative detention” -- were blocked on Sina Weibo.

Perhaps most significant were those tweets that dug into the excesses and perceived corruption of the local government that persecuted Yang. Many users pointed out that Zhangjiachuan has been designated a state-level poverty-stricken county, entitling it to extensive government aid that -- based on online searches -- has been wasted on vanity projects. Some netizens circulated an image of a vast, posh conference room that they claimed belonged to the local party secretary.

“Who says Zhangjiachuan is a poverty-stricken county?” asked a Sina Weibo microblogger in Wenzhou on Sunday night. Another Weibo user, also posting Sunday evening, tweeted five specific allegations against the local government, including a suggestion -- based on old documents uncovered by microbloggers -- that the local police chief had bribed his way into his job. That post garnered more than 14,900 re-tweets and 5,600 comments but it was neither deleted nor has it generated any form of prosecution.

Instead, these tweets seem to have produced results. Early Monday morning, Yang was released from detention. Shortly after, the earnest looking young man posed for a photo making a defiant “V” for victory sign. Later that day, the local government’s website announced that Zhangjiachuan’s police chief had been suspended. Court records that have turned up show that the police chief gave the equivalent of about $8,000 to his boss over 10 years -- no explanation was given for the bribes, though the boss was sentenced to 12 years in jail for taking them back in April.

As progress for online free expression goes, this is minor. Zhangjiachuan is a small, unimportant locality far from Beijing. Punishing its officials -- and freeing its junior-high students -- means almost nothing to national leaders who have spent the last two months tightening their control of the Internet. Arguably, Yang’s freedom actually enhances the government’s case for the rules by suggesting that they’ll be applied reasonably, contrary to widespread fears.

There should be no question about the Communist Party’s determination to keep up its anti-rumormongering campaign. Major state-owned newspapers have expressed support for upholding the rules, regardless of the age of the accused. And even young Yang, triumphant as he left detention, seems to have developed a better appreciation for the government’s bottom-line on information control. According to an official statement by the Zhangjiachuan government, he confessed his offenses before his release. In the interview with the Beijing News, Yang was asked how his experiences may have changed him. “I’ll continue to follow microblogs, but my posting will be more cautious, based on verifiable evidence, and devoid of foul language,” he answered, no doubt delighting his jailers.

For now, there doesn’t seem to worry about: As of Wednesday, Yang’s microblogging accounts remain deleted.

(Adam Minter, the Shanghai correspondent for the World View blog, is writing “Junkyard Planet,” a book on the global recycling industry.)

To contact the author of this article: Adam Minter at ShanghaiScrap@gmail.com

To contact the editor responsible for this article: Zara Kessler at zkessler@bloomberg.net