The "Great Firewall" just got a lot harder to break through.
Services helping Chinese users circumvent the “Great Firewall of China” have been pulled from Apple’s Chinese App Store en masse.
On Saturday morning, at least some software makers affected by the sweep received notification from Apple that their tools were removed for violating Chinese law.
Internet censorship in China restricts communications about topics including democracy, Tibetan freedom, and the 1989 Tienanmen Square protests.
The culling primarily seems to have affected virtual private networks, or VPNs, which mask users’ Internet activity and data from outside monitoring. According to a report by the New York Times, many of the most popular such apps are now missing from the Chinese App Store.
Two affected companies, ExpressVPN and Star VPN, claim that all major VPN apps for iOS have been pulled.
Get Data Sheet, Fortune’s technology newsletter.
ExpressVPN reminded Chinese users that they could access App Stores outside of China by listing a foreign billing address, and that their apps for Windows, Android, and – intriguingly – Mac operating systems remained available.
In an emailed statement on the matter, Apple wrote: “Earlier this year China’s MIIT [Ministry of Industry and Information Technology] announced that all developers offering VPNs must obtain a license from the government. We have been required to remove some VPN apps in China that do not meet the new regulations. These apps remain available in all other markets where they do business.”
Apple also recently announced it would build a Chinese data center that would store user data collected locally. That move came in response to new Chinese cybersecurity rules, though the company insisted the Chinese government has no access to user data.
Apple’s push for compliance come as it faces headwinds in the Chinese smartphone market. Chinese iPhone revenues, which for years were a major source of growth for Apple, have dropped recently thanks to both the rise of cheaper competitors and the wait for a new iPhone model.
One prominent and controversial champion of Internet freedom, the former NSA contractor Edward Snowden, quickly responded with outrage to Apple’s move. “Dollars can’t wash out be stain,” he wrote on Twitter.
This story has been updated with comment from Apple.