“Under the law, the person running the Department of Justice must have been approved by the United States Senate for some previous position. Even on an interim post,” Napolitano told Fox News ’ Dana Perino.

Former Attorney General Jeff Sessions was dismissed on Wednesday and Napolitano said his interim replacement should have been Deputy Attorney General Rod Rosenstein .

While Whitaker was confirmed by the Senate in 2004 when he was appointed U.S. Attorney for the Southern District of Iowa, Napolitano said that he was nevertheless ineligible to serve in his current post as the confirmation was not “for a leadership position in the Justice Department.”