In a case watched closely as a test of online freedom of speech, Twitter's attorney Benjamin Lee said in a tweet: "We're appealing the Harris decision. It doesn't strike the right balance between the rights of users and the interests of law enforcement."
The announcement came weeks after Manhattan criminal court Judge Matthew Sciarrino ruled that law enforcement had the right to see tweets and other user data from Malcolm Harris, who is being prosecuted for disorderly conduct in connection with an Occupy protest on the Brooklyn Bridge last year.
The judge said that the tweets are not private information and thus not subject to the constitutional guarantee of privacy.
"If you post a tweet, just like if you scream it out the window, there is no reasonable expectation of privacy," he said in an 11-page ruling.
The American Civil Liberties Union and others have cited the case as a test of free speech online. The ACLU said it hopes the decision is eventually overturned.