(CNN) Pope Francis earned a standing ovation when he told Congress in 2015 that he supports protecting human life "at every stage of its development." When he added that "this conviction" includes working to end the death penalty, the response was far more subdued.

"You didn't see people jumping up and clapping," said John Carr, who was in the room, and is director of Georgetown University's Initiative on Catholic Social Thought and Public Life.

For decades, Catholic politicians who support capital punishment, including the senators and representatives in the chamber that day, had an "out" when it comes to church teaching: The Catholic Catechism, the church's book of moral and religious teachings, had allowed the use of capital punishment in certain cases. Any other opinions, even the Pope's, were just that, opinions, and not necessarily binding on Catholic consciences.

But that is no longer the case, the Vatican announced on Thursday.

At the Pope's direction, the Catholic Catechism has been revised, and now calls the death penalty "inadmissible." While years in coming, the shift raises new questions about how politicians, particularly conservative Catholics in red states, will navigate the church's revised stance.

"Pope Francis has said several times that he considers the death penalty inadmissible," said John Thavis, former Rome bureau chief for Catholic News Service. "Now, however, he has enshrined it in official Catholic teaching. That's going to make it much more difficult for politicians to dismiss this teaching as 'the Pope's opinion.'"

The church's shifting position on capital punishment may even arise later this year when the Senate holds confirmation hearings for Brett Kavanaugh, a federal judge and faithful Catholic whom President Donald Trump has nominated for a seat on the Supreme Court.

"It's hard to side-step this issue now that it's definitive church teaching," said John Gehring, a Catholic writer and Catholic Program Director at the liberal-leaning group Faith in Public Life.

"I think there is a proper and respectful way to ask Kavanaugh how his understanding of faith and morality intersects with his judicial views."

"I suspect that the matter will come up," agreed Richard Garnett, a professor at the University of Notre Dame's law school. "I'm not optimistic that any senator's question will reflect any serious engagement with, or understanding of, what Pope Francis actually did, but ... I expect it will come up."

If confirmed, Kavanaugh would be the fifth Catholic on the Supreme Court, which regularly opines on death penalty cases and hears requests for stays of execution. (It is unclear whether Neil Gorsuch , who was raised a Catholic but has worshiped in Episcopal Churches, identifies with either tradition.)

The death penalty was a controversial subject during the Senate's confirmation hearings last year for Amy Coney Barrett, who now serves on the US Court of Appeals for the 7th Circuit. Noting an article Barrett wrote examining whether Catholic judges should recuse themselves from capital punishment cases, Sen. Dianne Feinstein famously said, "The dogma lives loudly within you."

Quiet conservatives

Among Americans, 54% favor the death penalty for people convicted of murder, while 39% are opposed, according to a Pew Research Center survey conducted in April and May. Among Catholics, the survey found that 53% of Catholics favor capital punishment, while 42% oppose it.

Death penalty opponents celebrated the Vatican's announcement, calling it the culmination of years of planning and work, while hoping it could change more attitudes among lay Catholics.

"For people in the pews, it is a challenge to actively build a culture of life by abolishing the death penalty, especially in the 31 states that still have it on the books in this country," said Krisanne Vaillancourt Murphy, who leads Catholic Mobilizing Network, an anti-death penalty group.

Many conservative Catholics, meanwhile, were mostly quiet on Thursday. Several prominent legal and political figures did not respond immediately for comment. But in the past, several Catholic governors had said that the Catechism gave them leeway to enforce the death penalty.

Gov. Greg Abbott of Texas, whose state overwhelmingly supports capital punishment according to polls, told journalists in 2014 that there's no conflict between his Catholic faith and state law on the issue.

"Catholic doctrine is not against the death penalty, and so there is no conflict there," he said.

Likewise, Nebraska Gov. Pete Ricketts, who is Catholic and lobbied against a state ban on the death penalty, has said capital punishment can be justified.

"The Catholic Church does not preclude the use of the death penalty under certain circumstances: That guilt is determined and the crime is heinous. Also, protecting society," Ricketts said in 2015

Abbott and Ricketts' offices did not immediately respond to requests for comment.

On Thursday, Sister Helen Prejean, a prominent opponent of capital punishment, called on Ricketts to fall in line with the Pope and cancel planned executions.

Will Catholic @GovRicketts, who spends a lot of time talking about his "pro-life values," heed the words of Pope Francis by cancelling the experimental execution scheduled for August 14 in Nebraska? #DontKillForNE — Sister Helen Prejean (@helenprejean) August 2, 2018

Nebraska's three Catholic bishop echoed Prejean's call to cancel the execution and urged Catholics and others to lobby state officials.

"Simply put, the death penalty is no longer needed or morally justified in Nebraska," the bishops said

What the Catechism says now

"Recourse to the death penalty on the part of legitimate authority, following a fair trial, was long considered an appropriate response to the gravity of certain crimes and an acceptable, albeit extreme, means of safeguarding the common good," the Catechism will now say.

But an "increasing awareness" that criminals don't lose their human dignity, a "new understanding" of prison systems and the development of "effective systems of detention" have led the church, under Pope Francis, to revise its official views, the Vatican said.

"The death penalty is inadmissible because it is an attack on the inviolability and dignity of the person," the Catechism will now say.

Does all of this mean that Catholic politicians will immediately switch positions on the death penalty?

Don't bet on it, said Helen Alvaré, professor of law at the Antonin Scalia Law School at George Mason University.

"The death penalty teaching may be observed or ignored, as is the abortion teaching, even though both are about killing," Alvaré wrote in an email.

"Politicians of any religion seem to variously ignore, observe both as a matter of consistency, or take inconsistent positions!"