Special Counsel Robert Mueller is "going well beyond his authority as a prosecutor," the Harvard law professor emeritus and lifelong Democrat told "Outnumbered Overtime" on Monday.
Mueller has requested documents from the Justice Department regarding the president's firing of FBI Director James Comey and Attorney General Jeff Sessions' recusal from the Russia probe. He is scheduled to interview several White House officials.
"The president is entitled to fire the head of the FBI," Dershowitz said. "The president is entitled to direct his attorney general who to investigate, who not to."
"That's what the law has been since Thomas Jefferson," he added, saying that if we want to change it we must do so in the legislative arena, not through a prosecutor.