During his younger days, Kirby worked at the United States Department of Justice as the special assistant to the head of the Civil Rights Division, John Doar, during the height of the civil rights movement in the 1960s. At the Department of Justice, where he first worked as a summer intern, he gathered voting records throughout the South that demonstrated evidence of widespread discrimination against African-Americans. His documentation of methods such as literacy tests specifically designed to exclude African-Americans from voting helped form the basis of the Voting Rights Act of 1965. While at the Civil Rights Division, he also found himself personally escorting African-American children into segregated schools, surrounded by federal marshals. Later, he was appointed Deputy Director to the President's Commission on Campus Unrest, founded in the aftermath of the killings of four students at Kent State University.