Justice Samuel A. Alito Jr. warned an audience in Rome on Saturday that he believes religious liberty is embattled across the globe.

To the extent religious freedom is under pressure in the United States and Europe, the U.S. Supreme Court justice said, it “pales in significance” compared to what is happening in countries like Nigeria, China and Iraq.

“It is a great matter of concern and something that I think all Christians should be concerned about and should try to find ways of combating this problem,” Justice Alito said during an event cosponsored by the United States Embassy to the Holy See, the Vatican and the U.S. Conference of Catholic Bishops. The event was part of the Jubilee, the church’s yearlong festival of faith, penance and forgiveness of sins that takes place every quarter century.

During a nearly hourlong conversation on Saturday afternoon in the Palazzo della Cancelleria in central Rome, which houses the Supreme Court of the Vatican, Justice Alito spoke with Monsignor Laurence Spiteri, justice emeritus of the Vatican appeals court that rules mostly on marriage annulments. Justice Alito, a conservative Catholic, talked about Christians being murdered in Nigeria but also referred to the oppression of Muslim Uyghurs in China and attacks on Muslim sects in Iraq under the Islamic State terrorist group.

In the morning, Justice Alito also briefly spoke with Pope Leo XIV during an audience in St. Peter’s Square for the pilgrims who had come to Rome for the Jubilee.

Justice Alito has visited Rome for decades, often teaching or participating in academic conferences, according to his annual financial disclosures. This trip coincided with the so-called Jubilee of Justice, during which Catholics from the legal profession are making pilgrimages to the Vatican. It was also the first significant event hosted by Brian Burch, the U.S. ambassador to the Holy See, who recently arrived to take up his post in Rome.

Responding to a question about the connection between Catholic history and civil governance, Justice Alito said Supreme Court justices “do not have divine authority and I hope we never stray into thinking that we do.”

He added that, as a Catholic, he saw his faith as compatible with his profession.

“I think reason is a hallmark of the Catholic intellectual tradition,” he said, noting that he believed this made his religion “entirely compatible” with his role as a secular judge in a country that separates church and state.

He spoke of several cases regarding religious freedom in the United States that have come before the court, including a decision he wrote allowing parents with religious objections to storybooks with L.G.B.T.Q. themes to withdraw their children from public school classes when the books are discussed, and a ruling that said the state of Maine could not exclude religious schools from a state tuition program.

Catholics now have a strong presence on the U.S. court. All six of the conservative justices, as well as a liberal justice, Sonia Sotomayor, either are practicing Catholics or were raised in the faith. Justice Alito has written for the majority in opinions on some of the court’s most momentous decisions in recent decades, including the 2022 decision to overturn Roe v. Wade and eliminate the constitutional right to abortion and the 2014 ruling in which the court said requiring family-owned corporations to pay for insurance coverage for contraception violated a federal law protecting religious freedom.

Sitting in the audience on Saturday evening in a chamber lined with frescoes by the Renaissance painter Giorgio Vasari were lawyers from the United States who came to Rome on a pilgrimage with the Catholic Bar Association. Cardinal Raymond Burke, a leading conservative Catholic, and Martha-Ann Alito, the justice’s wife, were also in the room. Journalists were not permitted to ask questions, but Monsignor Spiteri asked several previously submitted queries that were from members of the audience.

It was not clear who had arranged for Justice Alito’s travel. Several months ago, the U.S. Embassy to the Holy See extended invitations to all nine justices of the Supreme Court, starting with Chief Justice John G. Roberts, Jr.

The court did not respond to a request for comment.

The Rev. Paul B.R. Hartmann, associate general secretary of the U.S. Conference of Catholic Bishops, said Justice Alito had already planned to be in Rome.

“I think it just kind of worked out that this was an opportunity that he felt was fortuitous that he could be there in Rome and do this,” said Father Hartmann.

Joshua M. McCaig, a commercial lawyer from Kansas City, Mo., and founding president of the Catholic Bar Association, also said Justice Alito was in Rome for a separate event, though neither Mr. McCaig nor Father Hartmann knew what the other event was.

Justice Alito has strong family ties to Italy. He grew up in an Italian-American family in New Jersey, the child of an Italian immigrant father. Justice Alito has often spoken of his father, Samuel Alito Sr., who was born in Calabria in southern Italy, as his role model. On Saturday, in response to a question about who had most influenced his Catholicism, Justice Alito said his mother was his “first teacher in many things, including in the faith.”

As an undergraduate at Princeton, Justice Alito wrote a historical study of Italy’s Constitutional Court, concluding that the country’s high court was “deeply divided along lines of ideology and partisan politics; that the justices vote according to their politics on most cases; and that the various factions attempt to form coalitions in order to assemble a majority.”

In a yearbook entry, Justice Alito wrote that he researched the paper “in various sidewalk cafes in Rome and Bologna during the summer of 1971,” according to The Daily Princetonian.

The justice has continued his travels to Italy since joining the Supreme Court in 2006. Some of his trips have stirred considerable controversy. It was in Rome, sometime between 2016 and 2019, that the justice struck up a friendship with Princess Gloria von Thurn und Taxis, a conservative Catholic and divisive figure in her native Germany for her ties to the country’s far right. The princess, who has called the justice “a hero,” invited him to her 500-room palace in Bavaria, where they attended an opera festival dedicated to the work of the German composer Richard Wagner.

In July 2022, weeks after he wrote the majority opinion overturning Roe v. Wade, Justice Alito gave a speech at a religious liberty conference in Rome where he mocked critics of the decision, including Britain’s Prince Harry.

“I had the honor this term of writing, I think, the only Supreme Court decision in the history of that institution that has been lambasted by a whole string of foreign leaders, who felt perfectly fine commenting on American law,” he said during the speech.

The domestic political circumstances in the United States have shifted since that visit by Justice Alito to Rome. President Trump is back in the White House and the Supreme Court has regularly sided with the president.

This time, the side that Justice Alito “identifies with is in political power, and aggressively in political power,” said Ira C. Lupu, an emeritus professor at George Washington University Law School who specializes in religion.

Justice Alito said in his remarks that the president, as leader of the executive branch, is “someone who has discretion to enforce the law” and “should be enforcing the law with mercy.”

Josephine de La Bruyère contributed reporting from Rome.