The U.S. Department of Justice and the FBI believe they don’t need a search warrant to review Americans’ e-mails, Facebook chats, Twitter direct messages, and other private files, internal documents reveal. Government documents obtained by the American Civil Liberties Union and provided to CNET show a split over electronic privacy rights within the Obama administration, with Justice Department prosecutors and investigators privately insisting they’re not legally required to obtain search warrants for e-mail. The IRS, on the other hand, publicly said last month that it would abandon a controversial policy that claimed it could get warrantless access to e-mail correspondence. The U.S. attorney for Manhattan circulated internal instructions, for instance, saying a subpoena — a piece of paper signed by a prosecutor, not a judge — is sufficient to obtain nearly “all records from an ISP.” And the U.S. attorney in Houston recently obtained the “contents of stored communications” from an unnamed Internet service provider without securing a warrant signed by a judge first.