College and universities have long been hubs of free speech -- and hotbeds of protest. In this 1964 photo, civil rights groups picket a speech by Alabama Gov. George Wallace at the University of Cincinnati in Cincinnati, Ohio. The controversial Wallace, a leading spokesman for segregation, denounced a newly passed civil rights bill as a federal power grab. Gene Smith/AP

James Meredith is accompanied by two federal marshals and surrounded by jeering students after registering for entry at the University of Mississippi in the fall of 1962. The first African-American student to enroll at the school, Meredith suffered constant harassment on campus before graduating the next year. Francis Miller/The LIFE Picture Collection/Getty Images

College students from various nearby schools march down Commonwealth Avenue in Boston in October of 1965 to protest US involvement in Vietnam. Several hundred students -- most from Boston University, Harvard and MIT -- marched in the parade before attending a rally on Boston Common. Frank C. Curtin/AP

In 1968 students at Columbia University in New York took over four buildings on campus to protest the school's affiliation with the Institute for Defense Analyses, a weapons research think tank. The students were also protesting Columbia's plan to construct a segregated gymnasium in the city-owned Morningside Park. The sit-in ended violently when police stormed the buildings. Bettmann/Getty Images

Mario Savio, right, one of the leaders of the 1964-65 Free Speech Movement at the University of California-Berkeley, speaks at a "Peoples Park" rally on campus in June 1969. The movement, which protested the university's ban on student political activity, soon spread to other campuses. Slava J. Veder/AP

Dorothy Goldsmith and Rita Webb squirt Kenneth Opat with oil in 1970 at Tulane University in New Orleans, where students tagged Louisiana's oil industry with the "polluter of the month" award. The demonstration on April 22 of that year was part of the first annual observance of Earth Day. Associated Press

Mary Ann Vecchio screams as she kneels by the body of student Jeffrey Miller, shot by National Guardsmen on May 4, 1970, on the campus of Kent State University in Kent, Ohio. The National Guard had been called in to help quell several days of unrest on campus by crowds of demonstrators protesting the war in Vietnam. This photo was published worldwide, won a Pulitzer and helped sway public sentiment against the war. John Filo/AP

A group of anti-apartheid demonstrators find themselves blocked off behind the municipal building in Berkeley, California on April 18, 1985, after marching from campus to a courthouse where 20 demonstrators were awaiting arraignment. The protesters became trapped in an alley after police closed a gate on them. Ron Tussy/ASSOCIATED PRESS

A teddy bear adorns one more than 400 panels of the AIDS Memorial Quilt as volunteers stand by silently during a 1996 ceremony at Elmhurst College in Elmhurst, Ilinois. BETH A. KEISER/Associated Press

New York University students lay down to form a peace symbol on the floor of the NYU library in 2003 to protest the impending war in Iraq. Stephen Chernin/Getty Images

University of Missouri graduate student Jonathan Butler, second from right, speaks on November 9, 2015, following the announcement that University of Missouri System President Tim Wolfe would resign. Wolfe stepped down amid widespread protests over his handling of racial tensions at the Columbia, Missouri school. Sarah Bell/Missourian/AP

Yale University students and faculty rally November 9, 2015, to demand the school become more inclusive to all students. The "March of Resilience" followed several racially charged incidents at Yale, including allegations that a fraternity turned a woman away from a party because she was not white. Arnold Gold/New Haven Register/AP

A student walks by a bulletin board November 12, 2015, at Yale University in New Haven, Connecticut. More than 1,000 students, professors and staff at Yale gathered to discuss race and diversity at the Ivy League school amid a wave of demonstrations at US colleges over the treatment of minority students. Shannon Stapleton/Newscom/REUTERS

Columbia University students gather to protest President Donald Trump's executive order on immigration January 30, 2017, in New York. The executive order banned travelers to the US from seven predominantly Muslim countries. Frank Franklin II/AP