"As we continue to grow internationally, we will enter countries that have different ideas about the contours of freedom of expression. Some differ so much from our ideas that we will not be able to exist there," the company said. "Others are similar but, for historical or cultural reasons, restrict certain types of content, such as France or Germany, which ban pro-Nazi content."
Twitter said it has not yet used the ability, which is outlined on its Help page, but when it does it will try to retroactively notify the sender. The company also announced an expanded agreement with Chilling Effects, a blog monitoring Internet legal activity and censorship, to increase Twitter's transparency on free expression issues.
Update: In an email, Twitter spokesperson Jodi Olson said the company was not backing off its commitment to free expression.
"Just to be clear, this is not a change in philosophy and there are still countries to which we will not go," Olson said. "We hold freedom of expression in high esteem and work hard not to remove Tweets."
The three major, U.S.-based social networks are all currently banned in China, a country analysts all agree is crucial for future growth. While Twitter's post did not specifically mention China, it clearly positions the company ahead of Facebook and Google+ in articulating a career policy for handling content that may rile Chinese government officials.
While the Great Firewall of China currently blocks most of China's 500 million Internet users from accessing the service, some tech-savvy Chinese citizens have managed to work around the firewall to access Twitter. It's not clear if Twitter's new policy will impact those users.
Twitter has previously been a stalwart in protecting free speech. In making today's announcement, Twitter even a year-old blog post in which it said it would allow tweets to continue flowing even as Arab Spring uprisings escalated in Egypt. "There are Tweets that we do remove, such as illegal Tweets and spam," the company said at the time. "However, we make efforts to keep these exceptions narrow so they may serve to prove a broader and more important rule--we strive not to remove Tweets on the basis of their content."
Update: "This launch gives us the ability, when we have to, in response to a valid legal request, withhold a Tweet in a specific country and to keep that Tweet visible for the rest of the world," Olson said Thursday. "Our policy in these cases is to 1) promptly notify the affected users, unless we are legally prohibited from doing so; 2) withhold the content in the required countries only, rather than worldwide; 3) clearly indicate to viewers that a Tweet or Account has been withheld, and 4) make available any requests to withhold content through our partnership with Chilling Effects."