In a courtroom filled with vociferous tax opponents, a federal judge extended a temporary ban on a book that argues Americans do not have to pay income taxes.

Senior U.S. District Judge Lloyd D. George asked attorneys Friday to submit more information by May 1 before he decides whether to permanently ban Irwin Schiff's "The Federal Mafia: How It Illegally Imposes and Unlawfully Collects Income Taxes."

The American Civil Liberties Union of Nevada filed a friend-of-the-court brief saying the 75-year-old's opinions should not be suppressed.

"A total ban on a book containing political and autobiographical [elements] is unconstitutional," ACLU lawyer Allen Lichtenstein said outside court.

The federal government argues that the First Amendment does not protect speech advocating illegal conduct.

Department of Justice lawyer Evan Davis said Schiff had 3,100 clients attempting to evade $56 million in taxes. He has called Schiff's work one of the largest tax scams in U.S. history.

The Internal Revenue Service raided Schiff's Las Vegas business, Freedom Books, on Feb. 11. After the government filed a civil complaint against Schiff and two associates, the judge issued a temporary order banning Schiff's book.