When he said he would ensure they were pro-life, he meant it

Ms. Barrett told the senators that she was a faithful Catholic, and that her religious beliefs would not affect her decisions as an appellate judge. But her membership in a small, tightly knit Christian group called People of Praise never came up at the hearing, and might have led to even more intense questioning.

Some of the group’s practices would surprise many faithful Catholics. Members of the group swear a lifelong oath of loyalty, called a covenant, to one another, and are assigned and are accountable to a personal adviser, called a “head” for men and a “handmaid” for women. The group teaches that husbands are the heads of their wives and should take authority over the family.

Current and former members say that the heads and handmaids give direction on important decisions, including whom to date or marry, where to live, whether to take a job or buy a home, and how to raise children.

Legal scholars said that such loyalty oaths could raise legitimate questions about a judicial nominee’s independence and impartiality. The scholars said in interviews that while there certainly was no religious test for office, it would have been relevant for the senators to examine what it means for a judicial nominee to make an oath to a group that could wield significant authority over its members’ lives.

“These groups can become so absorbing that it’s difficult for a person to retain individual judgment,” said Sarah Barringer Gordon, a professor of constitutional law and history at the University of Pennsylvania. “I don’t think it’s discriminatory or hostile to religion to want to learn more” about her relationship with the group.

Ms. Barrett, through a spokesman at the Notre Dame Law School, where she is on the faculty, declined several requests to be interviewed for this article.

A leader of the People of Praise, Craig S. Lent, said that the group was not “nefarious or controversial,” but that its policy was not to confirm whether Ms. Barrett or anyone else was a member. Mr. Lent, whose title is overall coordinator and who has belonged to the group for nearly 40 years, said in interviews that the group was about building community and long-term friendships, and that members have a “wide spectrum” of political views.

“We don’t try to control people,” said Mr. Lent, who is also a professor of electrical engineering and physics at Notre Dame. “And there’s never any guarantee that the leader is always right. You have to discern and act in the Lord.”

He later added, “If and when members hold political offices, or judicial offices, or administrative offices, we would certainly not tell them how to discharge their responsibilities.”