If legally required, Twitter can selectively block tweets from appearing in a specific country. That is to keep the messages flowing. It was noted before that Twitter said that if it’s required to remove messages, they could do it globally.
This is what Twitter has to say on its blog:
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. Others are similar but, for historical or cultural reasons, restrict certain types of content, such as France or Germany, which ban pro-Nazi content.
Until now, the only way we could take account of those countries’ limits was to remove content globally. 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.
One of our core values as a company is to defend and respect each user’s voice. We try to keep content up wherever and whenever we can, and we will be transparent with users when we can’t. The Tweets must continue to flow.
Notably, China blocks Twitter which is described as unfortunate and disappointing” by the co-founder Jack Dorsey.