The University of California at Berkeley is again blocking a conservative speaker from coming to the flagship public campus, an advocacy group claimed, threatening the constitutional rights of students.

But university officials said they welcome Ben Shapiro. “We’re going to make this work, and provide the security that is necessary,” university spokesman Dan Mogulof said Wednesday evening. The largest spaces on campus available free of charge are booked that night, he said, but other sites, including some that require a rental fee, are available.

“We really need to speak with them and work with them and would much rather be doing that than responding to press releases.”

Berkeley, long known for its liberal-leaning student body and its role in the Free Speech Movement of the 1960s, has become a cultural battleground, with pitched fights between far-left and far-right activists.

When Milo Yiannopoulos, a writer who calls himself a free-speech fundamentalist and whom critics call a hatemonger, tried to speak on campus in February, University of California police locked down the campus and canceled the event after 150 or so “black bloc” anarchists in masks streamed into a large crowd of peaceful student protesters, breaking windows, setting a propane tank ablaze and attacking police with rocks and firecrackers.

That decision was polarizing: Some saw it as the smothering of conservative thought, an assault on the First Amendment. Others saw it as the only rational response to the imminent threat of dangerous riots.

President Trump jumped into the fray with a tweet the morning after: “If U.C. Berkeley does not allow free speech and practices violence on innocent people with a different point of view — NO FEDERAL FUNDS?”

In the months to come, there were violent clashes between far-right and far-left protesters in Berkeley. The Berkeley College Republicans, who had invited Yiannopoulos, asked conservative commentator Ann Coulter to speak on campus, and that sparked another fight, as campus officials canceled the event over safety concerns.

After pushback, they invited her to speak the following week in a safer venue. The Young America’s Foundation and College Republicans filed a lawsuit against the university, claiming it had violated their right to free speech.

Coulter never gave the speech.

This summer, Berkeley College Republicans, with the help of the conservative advocacy group Young America’s Foundation, invited Shapiro.

University officials said, when they learned of the invitation, that they welcomed him and would work to find a secure site for the speech.

Mogulof said Wednesday there are three venues on campus that are free to student groups and large enough to accommodate the event but that they were already booked for that time, so they have asked the student group if another time or a smaller venue would be acceptable or if they would be willing to pay to rent another space.

University officials asked the group in a letter this week to meet with campus police to talk about security issues. They said they had reserved smaller spaces for the night requested, and larger spaces on other nights, in hopes of ensuring Shapiro could speak.

“The university continues its shameful tactic of hiding behind vague security concerns,” Naweed Tahmas, external vice president of the UC Berkeley College Republicans, wrote in an email Wednesday night.

“Most recently, the university police and the administration cited broad concerns that Ann Coulter’s speaking engagement would spark violent protests.

“Ultimately, after massive police presence the day of Ms. Coulter’s proposed speaking date, the Anti-Fascists and other left-wing groups did not show. In fact, they released an op-ed stating that they had no intentions or plans to disrupt Ann Coulter’s speaking engagement at UC Berkeley. After canceling our last three events, UC Berkeley has solidified itself as an ideological echo chamber, as only favored viewpoints may be heard on campus with no meaningful opposition or challenge permitted. This is a disservice to students as it is incumbent upon universities to expose students to a breadth of different ideological views.”

The Young America’s Foundation announced: “Berkeley’s inability to find a lecture hall more than two months in advance is laughable.”

Shapiro, in a written statement, said, “Using ridiculous pretexts to keep conservatives from speaking is unsurprising but disappointing.

“We’ll find a way to get this event done, and UC Berkeley has a moral and legal obligation to ensure we do so.”

The university has a new interim policy for requests to host events. That includes previous elements, such as requiring advance notice, and commitments to free speech, emphasizing that speaker viewpoints won’t influence approval or security measures. There are new statements of the administration’s authority to require security that both ensures public safety and maximizes the right of sponsors to speak.

They support the right to have a wide variety of speakers on campus, and freedom of speech, Mogulof said.

“We want to have this event.” he said. “We want to support the students’ rights and ability to invite speakers of their choice.”