For generations, people in pews knew what to call it when folks "shacked up" before marriage -- "living in sin." "Sin" is a harder word to use, today.

The Catholic archbishop of Santa Fe, N.M., recently raised eyebrows with a mere letter reminding his flock that cohabitation is a grave sin that Catholics must take to confession or there will be eternal consequences. Archbishop Michael J. Sheehan's priests read his sobering words from their pulpits on April 3, the fourth Sunday of Lent -- the penitential season before Easter.

Those who cohabit, stressed Sheehan, are "objectively living in a state of mortal sin and may not receive Holy Communion. They are in great spiritual danger. At the best ... they are ignorant of God's plan for man and woman. At the worst, they are contemptuous of God's commandments and His sacraments. ...

"Often their plea is that they 'cannot afford a church wedding' i.e. the external trappings, or that 'what difference does a piece of paper make?' -- as if a sacramental covenant is nothing more than a piece of paper! Such statements show religious ignorance, or a lack of faith and awareness of the evil of sin."

In addition to forbidding known cohabiters from receiving Communion, Sheehan urged priests to avoid public scandal by refusing to commission them to serve Communion. After all, he said, "one commits the sin of sacrilege by administering a Sacrament in the state of mortal sin."

Also, priests should prevent those who cohabitate from serving as godparents for baptisms and confirmations, since the documents for these rites say it's "critical for the sponsor to be a practicing Catholic." How, Sheehan added, "can anyone be seriously called a practicing Catholic who is not able to receive the sacraments because they are living in sin?"

This latest Communion controversy is not taking place in a vacuum. American bishops continue to debate whether or not to deny Holy Communion to Catholic politicians who reject church teachings on hot-button issues such as abortion and same-sex marriage.

At the same time, Catholic leaders are making special efforts -- especially during Lent -- to draw Catholics back to confession or, as it is now known, the Sacrament of Penance and Reconciliation. After all, a 2008 study at Georgetown University's Center for Applied Research in the Apostolate found that 45 percent of American Catholics say they never go to confession and 12 percent say they go once a year. A generation or two after many Catholics lined up for confession on a weekly or monthly basis, a mere 2 percent say they participate in this sacrament once a month or more.

This is the context for Sheehan's letter, which raised additional issues central to the day-to-day lives of thousands of priests, parents and parish leaders. How should priests handle cohabitating couples that seek premarital counseling? Can these couples attend "Pre-Cana" programs for the engaged? How do priests convince these Catholics to seek forgiveness when they don't believe they are sinning?

Good luck with that, said commentator Heidi Schlumpf of the National Catholic Reporter. She gave Sheehan's letter a quick thumbs down, calling it a mere attempt to fire up traditionalists.

"I'm struck how un-persuasive this letter is," she wrote, online. "But then I wonder if that is its purpose. It seems Sheehan has no real interest in persuading or teaching, but rather only punishing those who disagree with him. Oh, and making those who already agree with him happy for 'laying down the law.' "

Father John Zuhlsdorf, author of the popular "What Does the Prayer Really Say?" weblog, stressed that the Santa Fe statement was blunt, but that silence and timidity would be even worse. The key, he said, is that Archbishop Sheehan dared to defend church teachings to the Catholics who are under this care.

"In this age of 'I'm OK, you're OK,' a bishop risks being called mean and uncompassionate if he does anything other than remain silent or wring his hands," said Zuhlsdorf, a former Lutheran who is completing his doctorate at the Patristic Institute "Augustinianum" in Rome.

"So how do you defend doctrines that many people think are offensive without committing what many people believe is the ultimate sin, which is offending people? ... Yet this is what bishops are supposed to do -- defend the teachings of the church. All of them. The whole package."