Following his term as attorney general, Clark taught courses at the Howard University School of Law (1969–1972) and Brooklyn Law School (1973–1981). He was active in the anti-Vietnam War movement and visited North Vietnam in 1972 as a protest against the bombing of Hanoi. During this time he was associated with the New York law firm Paul, Weiss, Rifkind, Wharton & Garrison, but he resigned in 1973, saying, "I didn't feel like working on things I didn't believe in, I didn't think were important."
