Facebook may be a global behemoth with 1.7 billion users, but there’s one huge market in which it has virtually no official presence: China. Chief executive Mark Zuckerberg has made no secret of his desire to enter the country, but so far his desire remains unrequited.

Now, the Facebook CEO appears to be planning to offer the Chinese government a gift, in the hope of winning its affections. According to the The New York Times, his team has developed a tool that will allow the state to censor content. But doing so will open a Pandora’s box that may be difficult to close.

Facebook already routinely censors content when asked to do so by governments, as does Twitter. But in most cases, this involves removing posts after the fact because they contravene a country’s laws. What it has apparently built for China would be prior restraint—censoring a post before it appears.

Zuckerberg has reportedly said it is better to be “enabling conversation” even if some of the conversation is censored, and it’s not surprising he would feel that way. His goal is to turn Facebook into a global town square. But what happens when some of the townsfolk suddenly disappear in the middle of the night, and you were the one who gave away their location?

Knowing that this kind of tool exists will also make it more difficult to stop other countries from asking to use it. What will Zuckerberg say if Russia or Turkey wants the same power of prior restraint? What does the global town square look like then?

***

The Data Sheet team wishes our U.S. readers a Happy Thanksgiving. The weekday edition returns Monday, Nov. 28.

Mathew Ingram
@mathewi
mathew.ingram@fortune.com