A campus protest that disrupted a guest lecture by an Israeli law professor has triggered a new debate about whether the University of Minnesota is doing enough to protect free speech.

Dale Carpenter, a U law professor, took to a national blog on Wednesday to denounce what he called attempts to shut down "the free exchange of ideas" on campus.

Moshe Halbertal, a law professor from Hebrew University in Jerusalem, was about to begin a lecture at the law school Tuesday afternoon when a series of protesters began shouting him down, according to Carpenter, who was in the audience.

He said the speech was delayed more than half an hour until police cleared the protesters from the lecture hall.

Three people, all nonstudents, were arrested and cited for trespassing, according to a university spokesman.

The protest was organized by a group called the "Anti-War Committee," and endorsed by a university group called Students for Justice in Palestine, which posted a photo and account of the incident on its Facebook page.

Moshe Halbertal was shouted down before beginning his talk, a U professor says.

Rula Rashid, a U finance major who is president of Students for Justice in Palestine, defended the protest. "The most patriotic thing you can do is protest something that shouldn't be happening on your campus," she said. Rashid, who said she is of Palestinian descent, called Halbertal an "apologist for war crimes," citing Israeli strikes on Gaza that killed thousands of people. "It doesn't make sense for us to stay silent," she said.

Halbertal had been invited to give a talk titled "Protecting Civilians: Moral Challenges of Asymmetric Warfare." He could not be reached for comment Wednesday.

Carpenter, a constitutional law expert, argued that the protesters crossed the line when they tried to stop Halbertal from speaking. "That the freedom to present a lecture is threatened in this way at a public university is appalling," he wrote Wednesday on a legal affairs blog on Washingtonpost.com.

In an interview, Carpenter said he saw it as a symptom of a larger problem on college campuses, "where people who feel they have a grievance, and who may have a grievance, think it's appropriate to prevent speakers from speaking about topics they're sensitive about," he said. He cited other incidents at the U, including an attempt by some faculty and students to revoke a 2014 speaking invitation to former Secretary of State Condoleezza Rice.

"It should concern anybody who supports freedom of speech," Carpenter said.

David Wippman, dean of the law school, issued a statement Wednesday condemning the protesters for trying to deny others the chance to hear "an invited guest." While protesting is also protected speech, he said, "it's not free speech when you silence others by shouting in the middle of a lecture."

He described Halbertal as "a well-known, widely respected expert on ethics and the law of war."

Carpenter wrote that Tuesday's lecture was "far more dovish and human-rights-oriented than caricatures of Halbertal as a 'war crimes apologist' by protesters suggested." Halbertal, who helped draft the ethics code for the Israeli army, argued that "professional combatants should err on the side of protecting noncombatants from casualties," Carpenter wrote, even if that means increasing "risks to themselves or to their cause."

Carpenter said the U should investigate and discipline any students who took part in the disruption.

Rashid said that some of the protesters were students, but "most of them were not."

The university said that it would investigate to determine if students violated the U's student code of conduct.

Wippman said that officials would review photos and videos of the event to try to determine who was involved. But he said he did not see this incident as evidence of a troubling pattern. "It's pretty well understood by the vast majority of the campus community that the U prizes the free exchange of ideas," Wippman said.

Steve Hunegs, executive director of the Jewish Community Relations Council, released a statement calling on the U "to publicly denounce these bullying tactics."

University President Eric Kaler and Provost Karen Hanson issued a joint statement Wednesday, saying: "A commitment to freedom of speech and thought is absolutely fundamental to the University of Minnesota. Our University is and must be a place where people can explore ideas, engage in vigorous debate, and learn from one another's perspectives."

Maura Lerner • 612-673-7384