BERKELEY, Calif. — The University of California, Berkeley, on Thursday reversed its decision to cancel a speech by the conservative author Ann Coulter, approving her to appear on campus in early May.
University administrators had said a day earlier that they could not let Ms. Coulter speak because of security threats. In a letter to the Berkeley College Republicans, who were sponsoring the speech, two vice chancellors said the university had been “unable to find a safe and suitable venue for your planned April 27 event featuring Ann Coulter.”
The decision was criticized not just by Ms. Coulter — who had vowed to defy the administration and speak at the university anyway — but also by groups and thinkers across the political spectrum who viewed it as an attack on free speech.
“Free speech is what universities are all about,” Robert Reich, a labor secretary in the Clinton administration and now a professor of public policy at Berkeley, wrote on his website. “If universities don’t do everything possible to foster and protect it, they aren’t universities. They’re playpens.”
The letter canceling the speech, written by Scott Biddy, a vice chancellor, and Stephen Sutton, the vice chancellor for student affairs, said it was “not possible to assure that the event could be held successfully — or that the safety of Ms. Coulter, the event sponsors, audience and bystanders could be adequately protected.”
The university had said it would try to reschedule the speech, perhaps in September. But on Thursday, it announced Ms. Coulter would be allowed to speak on May 2.
With Berkeley’s reputation as one of the country’s most liberal universities, the campus and surrounding areas have become a target for small, militant and shadowy right-wing groups that have clashed in recent months with equally militant and shadowy anarchist groups based in the San Francisco Bay Area.
On Saturday, at the latest of these violent encounters, the police arrested more than 20 people. One video that went viral on social media showed a man identified as a member of a white supremacist group sucker-punching a woman who identified herself as an anarchist. These fight-club-type episodes, both on campus and in the city of Berkeley, have escalated since President Trump’s election.
In February, a speech by the incendiary right-wing writer Milo Yiannopoulos, also sponsored by the College Republicans, was canceled after masked protesters smashed windows, set fires and pelted the police with rocks.
At a time of heightened polarization, Berkeley is not the only university struggling to balance free speech and security concerns. The police clashed with protesters on Tuesday outside an auditorium at Auburn University where the white nationalist leader Richard Spencer was speaking. The university had canceled the event on the grounds that it could turn violent, but a federal judge in Montgomery, Ala., ruled that the speech should proceed because there was no evidence that Mr. Spencer advocated violence.
The episodes have become fodder for conservative critics. In February, after the cancellation of the event with Mr. Yiannopoulos, Mr. Trump posted on Twitter, “If U.C. Berkeley does not allow free speech and practices violence on innocent people with a different point of view — NO FEDERAL FUNDS?”
Both Ms. Coulter and the Young America’s Foundation, which books her college speeches, had said they expected the event to proceed as planned. Spencer Brown, a spokesman for the Young America’s Foundation, which promotes conservative ideals, said in an email that Ms. Coulter’s lecture would take place next week “whether Berkeley likes it or not.”
PEN America, a literary and human rights organization that recently criticized Mr. Trump’s ban on travel from some majority-Muslim countries, also took issue with the university’s decision.
“For the University of California at Berkeley to declare a week ahead of time that maintaining safety and security in relation to Ann Coulter’s planned appearance on campus is impossible amounts to an unacceptable abdication of the crucial role of the university as an open forum for intellectual and ideological exploration,” the group’s executive director, Suzanne Nossel, said in a statement.
Mr. Reich, in his own statement, also let it be known what he thought of the speaker, while defending her right to speak, “How can students understand the vapidity of Coulter’s arguments without being allowed to hear her make them, and question her about them?”