AS A rule, the Majialou Relief and Assistance Centre offers neither relief nor assistance. An imposing complex of red seven-storey buildings, it stands next to an expanse of rubble and a few derelict houses on the south-western fringe of the capital. Few visit unless escorted by police. Few leave except in the custody of officials or their hired thugs. It is a clearing house for Beijing’s undesirables.

Majialou and another nearby centre, Jiujingzhuang, are at the hub of a network of extra-judicial detention facilities, authorised by the central government. Their aim is to keep the capital free of “petitioners” who come to Beijing to protest. The city also has many informal detention centres, known as “black jails”, run illegally at the behest of local governments, but to which the central government usually turns a blind eye. The network has been accused of dealing with the symptoms of anger in the provinces rather than its causes.

Tens of thousands of people arrive in Beijing every year to petition the central government, seeking redress for local injustices ranging from land seizures to police brutality. In the capital they are often detained by police and beaten. Once back in their hometowns some are sent without trial to labour camps as a warning not to try again.

Optimists, however, see signs that the central government is waking up to their plight. On February 5th a court in Beijing sentenced ten people to prison terms of up to two years for running a black jail. They had taken a group of petitioners, who had arrived in Beijing last April from the central province of Henan, from Jiujingzhuang relief centre to two black jails on the city’s edge. China Youth News, a Beijing newspaper, reported that some of the protesters were driven back to their hometown a day later. But they soon returned to Beijing where they told the police, who (remarkably) helped secure the release of the others. The sentences were not the first handed down to black jailers. But the unusual publicity the state-owned media gave to the case suggested a new determination by the central government to clamp down on the flourishing business.

Even if leaders are intent on a crack down, progress is likely to be slow. Black jails serve the interests of every level of government. Central officials want to keep complainants from coming to the capital and possibly forming a large and dangerous protest movement. The career prospects of lower-level leaders can be ruined by the appearance in Beijing of petitioners from their localities.

The relief centres at Majialou and Jiujingzhuang represent progress of sorts. Until ten years ago petitioners were often sent to “custody and repatriation” centres: in effect, jails where they, along with beggars and vagrants, could be held for weeks or even months in harsh conditions before being sent back to their hometowns. These facilities were scrapped in 2003 after an outcry over the beating to death of a university graduate in one of them in the southern city of Guangzhou.

But in the capital a new system was set up. Those found petitioning in “sensitive places”, such as Tiananmen Square, would be taken by police to a centre like Majialou where they would await collection by officials from their locality (or, more usually, by toughs recruited by local officials). As soon as a petitioner is admitted to one of the centres, the representative office in Beijing of that person’s home province is notified. In 2010 Beijing News quoted a provincial official saying that these offices are then under central-government orders to arrange for the petitioners to be removed within three hours.

Keep the wheels turning

Efforts to ensure a rapid turnover encourage provincial officials to use private security companies. These take the petitioners to black jails: usually houses in the suburbs or dingy guesthouses whose owners are paid to keep quiet. The petitioners are held (and sometimes roughed up) there until they can be transported back to their hometowns.

In 2010 the Chinese media exposed the case of a private-security company, with 3,000 black-clad employees, that had earned millions of dollars locking up petitioners on behalf of local governments. Another case came to light last year involving a group of black-jail operators that had whisked more than 1,000 people from Jiujingzhuang in 2010 and 2011. A Chinese journalist who has investigated the racket says occasional arrests of black-jailers have had no obvious impact on the lucrative business. Provincial officials continue to deploy private firms or gangs, often to seize petitioners from Beijing’s streets and put them directly in black jails.

Some petitioners scornfully refer to the relief centres themselves as black jails. Inside they are separated into different rooms according to their provinces. In Jiujingzhuang, petitioners say, mobile-phone signals are all but blocked. They are watched in their rooms by guards. No beds are provided: they have only hard benches to sleep on. “It is run like a detention centre,” says Zheng Yuming, a petitioner from the city of Tianjin who was taken to Majialou in November. Knowing that real black jails often await them, some petitioners try to resist being taken away. They are usually manhandled out.

The authorities show no sign of becoming any less zealous in rounding up protesters. Even if some of those running black jails are being punished, millions of dollars have recently been spent on upgrading and expanding the official centres that supply them with inmates. Government websites say that even before its expansion Majialou was processing an average of about 540 petitioners daily, and that as many as 7,000 people are employed by the facility. Beijing’s media say the centre is now designed to handle as many as 5,000 petitioners a day. It is not clear how often this number will be reached, but a government website said last June that petitioning visits to government offices in Beijing were “increasing dramatically”. Local governments are ill-equipped to cope by themselves, so black jails will remain in strong demand.

The heart of the problem is the party’s obsession with weiwen, or “stability maintenance”. In recent years local governments, state-owned enterprises and neighbourhood committees have set up a network of weiwen offices charged with looking out for signs of unrest. Spotting potential petitioners is one of their main tasks. On February 6th Pu Zhiqiang, a prominent Beijing lawyer, used three microblogs to attack China’s recently retired security chief, Zhou Yongkang, accusing him of having “inflicted torment” on the country with his weiwen efforts. Mr Pu’s accounts were soon shut down.