NYPD Battles Twitter for Identity of User Promising Violence 'Just Like in Aurora'

If Twitter were to turn over the user's identity at the first request, it could be liable for any mistake or potential invasion of privacy, according to Jennifer Granick, the director of civil liberties for Stanford Law School's Center for Internet and Society.

"The law prohibits providers from turning certain information over voluntarily and, if they do, they can be sued," Granick said. "But the government can compel the information from the provider with varying degrees of legal process depending on what the information is. When it's the name associated with the account, the government can get that with just the subpoena."