The dispute cuts to the core of the question of whether WikiLeaks allies are part of a criminal conspiracy or a political discussion. It also challenges the Obama administration's argument that it can demand to see computer data and read months' worth of private messages, even if they have nothing to do with WikiLeaks.
In court documents unsealed Tuesday, the three challenged a Dec. 14 court order forcing Twitter to tell the government the names of those they talk to privately and who follow their posts.
The information would allow the government to map out their entire audience and figure out where each person was when he logged on to Twitter, attorneys said, amounting to an intrusion on the First Amendment constitutional guarantee of free speech.
The documents echo the international debate WikiLeaks sparked when it began revealing a trove of sensitive military and diplomatic documents.
The U.S. is investigating whether WikiLeaks should be held responsible for leaking classified information, even though it was not the original leaker. Defense attorneys say it's a question of political discussion, arguing that Twitter communication about WikiLeaks is protected speech.
"The First Amendment guarantees their right to speak up and freely associate with even unpopular people and causes," attorneys wrote.
Aiden Fine, an attorney with the American Civil Liberties Union, said lawyers believe the government has also demanded similar information from other social networking sites and have asked a judge to make them public. Doing so would provide a rare glimpse at how widely the Obama administration believes it may trawl such sites for information.
The documents were filed by a member of Iceland's parliament and a former WikiLeaks activist, Birgitta Jonsdottir, as well as two computer programmers, Rop Gonggrijp and Jacob Appelbaum.
Attorneys said the demand for documents related to Jonsdottir raise their own unique concerns because she is a member of a foreign government. She uses her Twitter account primarily to discuss Icelandic issues, attorneys said, so the Justice Department's demand raises the possibility that foreign governments might make similar demands on members of Congress.
An e-mail seeking Justice Department comment was not immediately returned Tuesday.