The U.S. Department of Justice filed a “statement of interest” Thursday supporting a free-speech lawsuit by conservative students against the University of California.

It’s the third such legal filing the Trump administration has made in First Amendment cases since September, when U.S. Attorney General Jeff Sessions claimed that too many universities stifle conservatives’ free speech and singled out UC Berkeley.

In April, a student group, the Berkeley College Republicans, and their backers, the Young America’s Foundation, sued the University of California and UC Berkeley officials in federal court, accusing them of censorship against conservative students.

The students sued after the sides could not agree on when and where the Republican group could host right-wing commentator Ann Coulter on campus.

The times and places offered by the campus were intended to minimize the potential for student protests and rioting around Coulter’s visit. A few months earlier, in February, rioters did $100,000 in damage to the campus during a protest of another right-wing speaker, Milo Yiannopoulos. Campus officials said their restrictions were appropriate for “high-profile speakers.”

But the students said the campus’ offers for event times made it nearly impossible for students to attend — just before finals, when classes were suspended — and at places too far from the center of campus. Ultimately, Coulter never spoke on campus.

In September, U.S. District Judge Maxine Chesney said the students had failed to demonstrate that UC Berkeley had discriminated against them — but she gave the students a month to refile their lawsuit. They did so on Nov. 10. The university filed a motion to dismiss the case on Dec. 8.

Now, the Trump administration is weighing in on the students’ side with a “statement of interest” filing signed by Tara Helfman, a senior counsel in the Justice Department’s Civil Rights Division.

“This Department of Justice will not stand by idly while public universities violate students’ constitutional rights,” according to a statement issued Thursday about the department’s legal filing.

The Justice Department criticized the university’s high-profile speaker policy as discriminatory and arbitrary.

“A former president of Mexico and a former White House adviser were hosted at the University, but University administrators did not apply the High-Profile Speakers Policy to those events,” the statement said.

Legal filings of the kind filed Thursday by the Justice Department are similar to “friend-of-the-court” briefs that are intended to add weight to one side or the other in a legal dispute — but there is no rule requiring judges to give them any special consideration.

“There’s no obligation on the court except to read it,” said Pamela Karlan, a Stanford law professor and former Justice Department official in the Obama administration.

So the impact of the new filing depends on whether Chesney considers it persuasive.

UC Berkeley officials say the students’ allegations are unfounded.

“UC Berkeley does not discriminate against speakers invited by student organizations based upon viewpoint,” said Dan Mogulof, a campus spokesman. “The campus is committed to ensuring that student groups may hold events with speakers of their choosing, and it has expended significant resources to allow events to go forward without compromising the safety or security of the campus.

“This suit has already been dismissed by the Court once. The campus will continue to vigorously defend itself against these allegations.”

The Department of Justice has filed statements of interest in two other campus free-speech cases in which students at two public colleges, Georgia Gwinnett College and Los Angeles Pierce College, are challenging the school’s “free-speech zones” on campus. The cases are Uzuegbunam vs. Preczewski, and Shaw vs. Burke.

Nanette Asimov and Bob Egelko are San Francisco Chronicle staff writers. Email: nasimov@sfchronicle.com and begelko@sfchronicle.com Twitter: @NanetteAsimov and @Egelko