On a quiet Sunday morning in June, as worshippers settled into the pews at Allen Baptist Church in southwestern Michigan, Pastor Jason Burrick grabbed his cellphone and dialed 911. When a dispatcher answered, the preacher said a former congregant was in the sanctuary. "And we need to, um, have her out A.S.A.P."

Half an hour later, 71-year-old Karolyn Caskey, a church member for nearly 50 years who had taught Sunday school and regularly donated 10% of her pension, was led out by a state trooper and a county sheriff's officer. One held her purse and Bible. The other put her in handcuffs. (Listen to the 911 call)

The charge was trespassing, but Mrs. Caskey's real offense, in her pastor's view, was spiritual. Several months earlier, when she had questioned his authority, he'd charged her with spreading "a spirit of cancer and discord" and expelled her from the congregation. "I've been shunned," she says.

Her story reflects a growing movement among some conservative Protestant pastors to bring back church discipline, an ancient practice in which suspected sinners are privately confronted and then publicly castigated and excommunicated if they refuse to repent. While many Christians find such practices outdated, pastors in large and small churches across the country are expelling members for offenses ranging from adultery and theft to gossiping, skipping service and criticizing church leaders.

The revival is part of a broader movement to restore churches to their traditional role as moral enforcers, Christian leaders say. Some say that contemporary churches have grown soft on sinners, citing the rise of suburban megachurches where pastors preach self-affirming messages rather than focusing on sin and redemption. Others point to a passage in the gospel of Matthew that says unrepentant sinners must be shunned.