Speaking to about 800 students in Boulder Tuesday night, Ashcroft was repeatedly heckled. He ignored some hecklers and shot back retorts to others, The Denver Post reported.
The hecklers hooted and booed as Ashcroft defended the USA Patriot Act and the detention of terror suspects at a military prison in Guantanamo Bay, Cuba, The Rocky Mountain News said.
Ashcroft's composure broke at one point when a man loudly called him a liar.
"For those of you who have nothing to learn, why did you come tonight?" Ashcroft shot back.
Student security and Boulder police escorted several people out of the auditorium, but some managed to get back in, the Post said.
Ashcroft also drew shouts when he said national security had to be improved by focusing on the laws, but "never think outside the Constitution."
"Whooping and hollering in an auditorium will not get that done," he told the crowd.
Ashcroft served as attorney general in the Bush administration from 2001 until 2005.