China’s great firewall, a massive system of internet filters and blocking, has long had a crack in it. The firewall keeps most users in China from accessing platforms outside the country, such as Facebook, Google and Netflix, in keeping with China’s desire to censor what can be seen and read. But popular software known as virtual private networks permit a user inside China to tunnel through the firewall. Now the crack is being gradually cemented up.

A VPN has been particularly useful for foreign companies that come to China and want to link up with corporate networks outside it. Hoping to encourage such investment, China looked the other way for years at the existence of the VPNs, many available from Apple’s App Store in China. The VPNs are popular among millions of young people, as well as journalists and others.

China has been heading toward restricting them for some time, but now it is cracking down in earnest with a new cybersecurity law that carries criminal penalties. Apple informed more than 60 VPNs that they were being removed from the App Store in China on grounds that they were not licensed. Likewise, a Chinese company that operates Amazon’s cloud-computing business in China has sent a notice reminding customers to comply with local laws and cease using software such as VPNs that could pierce the Great Firewall. (Amazon founder Jeffrey Bezos owns The Washington Post.)

Apple, Amazon and other Western technology pioneers can have a positive influence on China, but the laws they obey can also become tools of censorship. Apple CEO Tim Cook said last week that Apple has been “engaging” with China over this “even when we disagree.” But there is no evidence that China’s leaders are prepared to loosen the reins of control. The trend is running the other way.