In another example of how tech companies are forced to navigate tricky waters in order to operate in China, Amazon Web Services recently started asking customers to stop using technology that can get around the Great Firewall of China.

The New York Times reported that Beijing Sinnet Technology, which is the local partner for AWS operations in China, sent out several emails over the last few days reminding its cloud customers that they’re not allowed to host technology, such as virtual-private networks (VPNs), which routes around China’s extensive system of networking monitoring and firewall technology. Apple has also come under scrutiny for removing several virtual-private network apps from its App Store in China in response to similar pressure from the government.

It’s just the latest in a series of events over the past decade highlighting the uneasy relationship between American tech companies and the Chinese government, which insists tech companies doing business in the country must follow its strict laws around censorship and content regulation. A new law that went into effect in June is said to be the impetus for the crackdown on VPN use, but Chinese regulators have been closely watching U.S. internet companies operating in China for over a decade.

Like many internet businesses, cloud computing in China is dominated by homegrown Chinese companies like Alibaba and Baidu, and the Big Three public cloud providers are pretty small inside China. Not only do these Chinese companies have close relationships with the government, but Chinese law prohibits AWS from using its own branding in China, forcing it to work through Beijing Sinnet Technology.

AWS representatives in the U.S. did not immediately respond to a request for comment on the emails sent by Beijing Sinnet.