SOUTH BEND, Ind. -- Nearly 40 people were arrested Sunday as they tried to enter the University of Notre Dame to protest President Obama's appearance at commencement, police said.

At least 39 people were taken into custody on trespassing charges, police Sgt. Bill Redman said. Among those arrested were Norma McCorvey, the plaintiff identified as "Roe" in the Roe v. Wade Supreme Court decision that legalized abortion. She now opposes abortion.

Obama's commencement speech capped weeks of protests at the nation's most prominent Roman Catholic university. Critics have condemned the university's decision to invite Obama, who supports abortion rights and embryonic stem-cell research, and some have called for the resignation of the Rev. John Jenkins, the university's president.

In his introduction for Obama, Jenkins reiterated the school's support for the church's teaching on the sanctity of human life but applauded Obama for coming to the school.

"Others might have avoided this venue for that reason, but President Obama is not someone who stops talking to those who differ with him," he said.

Obama thanked graduates for their "maturity and responsibility," acknowledging that his appearance "has not been without controversy."

Hundreds of people attended an outdoor Mass and rally on campus, while students who decided not to attend the commencement went elsewhere on campus for prayer. Students opposing the Obama invitation had urged peaceful protests.

Victor Saenz, a philosophy graduate from Mexicali, Mexico, said attending the ceremony "was something I just couldn't do" because he believed Obama's invitation violated a 2004 statement adopted by U.S. bishops saying Catholic institutions should not honor those who don't adhere to church teachings.

In his commencement appearance, Obama also received an honorary law degree.

Bishop John D'Arcy, whose diocese includes Notre Dame, joined the rally and called students "heroes" for expressing their anger over the invitation to Obama.

Some students who attended the rally carried signs declaring "Shame on Notre Dame" and "Stop Abortion Now." Many wore anti-abortion T-shirts, one of which depicted a leprechaun throwing a baby into a trash can and the words "May 17, 2009, The day the dome was forever tarnished," which referred to the school's famed golden dome.

Sunsara Taylor, a New York City resident and a member of the abortion-rights group Abortion on Demand, said outside the school's gates that "there was a voice missing" in the controversy over Obama's visit.

"If women don't have a right to decide if they have a child, women aren't free," she said. "We need to expand abortion access and abortion rights and lift the stigma. Fetuses are not babies and women are not incubators."

School spokesman Dennis Brown said most of the arrests Sunday were at the school's front gate, where most of the protesters angered by Obama's campus appearance had gathered.
He also said three people were ejected from the commencement venue after shouting anti-abortion slogans during Obama's speech.

Kathleen Hession, a graduate from Iowa City, Iowa, said after the ceremony that the protests have overshadowed the students' academic achievements.

"This is our graduation, and it's neither the time nor the place to stage something like that," she said. "I respect their beliefs, but it's not the right platform."