Starting today, we give ourselves the ability to reactively withhold content from users in a specific country — while keeping it available in the rest of the world. We have also built in a way to communicate transparently to users when content is withheld, and why.
We haven’t yet used this ability, but if and when we are required to withhold a Tweet in a specific country, we will attempt to let the user know, and we will clearly mark when the content has been withheld. As part of that transparency, we’ve expanded our partnership with Chilling Effects to share this new page, http://chillingeffects.org/twitter, which makes it easier to find notices related to Twitter.
Source: Twitter Blog