Pope Francis says any bishop who moves a suspected pedophile priest from parish to parish should resign.

Francis spoke about the church's handling of sex abuse cases while flying home Wednesday from Mexico, where victims of that country's most notorious pedophile, the Rev. Marcial Maciel, are still coping with the trauma of his abuse.

"It's a monstrosity," Francis said of clerical abuse. "Because a priest is consecrated to bring a child to God. And if he eats him in a diabolical sacrifice, it destroys him."

The role of bishops in the abuse scandal made headlines again recently after a French priest told a Vatican course for new bishops that they don't have to report suspected abuse to police. His comments drew a swift correction from Francis' top adviser, Cardinal Sean O'Malley, who said bishops have an "ethical and moral" obligation to report suspected pedophiles to civil authorities.

"A bishop who changes parish (for a priest) when he detects pederasty is reckless and the best thing he can do is present his resignation," Francis said. "Clear?"

Francis also reaffirmed the Vatican's oversight of Maciel's Legion of Christ, saying it is continuing to help the scandal-plagued religious order reform and praising his predecessor for bringing the truth of Maciel's misdeeds to light.

Maciel founded the Legion in Mexico in the 1940s, and it became one of the wealthiest and fastest-growing orders in the world. It is, however, emblematic of the Mexican church that Francis so acutely criticized during his trip, with close ties to Mexico's rich and powerful who by and large send their children to Legion-run schools.

The Vatican in 2010 took the order over after the Legion admitted, after decades of denial, that Maciel had sexually molested his seminarians and fathered at least three children.

Francis told reporters that the Vatican still plays a prominent role in running the order, even after it elected a new leadership 2014 and revised its founding constitutions. Francis recalled that while the superior general was elected from among rank-and-file Legion priests, he himself appointed the vicar, who also serves as a counselor on the governing board, as well as a second counselor.

He termed the status "semi-intervention."

"In this way, we are continuing to help them review their past," he said.

The Legion saga represents one of the gravest scandals of the 20th-century Catholic Church, emblematic of the way Church leaders protected their own at the expense of victims of clerical sex abuse. The scandal tarnished the legacy of St. John Paul II, since Vatican officials under his watch ignored credible allegations of Maciel's misdeeds and instead held him up as a model of religious orthodoxy who brought in vocations and donations.

Francis recalled that then-Cardinal Joseph Ratzinger, who was in charge of the Vatican office that handled sex abuse cases, had tried for years to sanction Maciel but was blocked. Francis didn't say by whom, but it is well known that John Paul's No. 2, Cardinal Angelo Sodano, prevented any action from being taken. Ratzinger later became Pope Benedict XVI, Francis' predecessor.

"Here, I'd like to pay homage to the man who fought at times when he didn't have the strength to impose himself until he could impose himself. Ratzinger. Cardinal Ratzinger. An applause for him," Francis said.

He said Ratzinger had gathered all the documentation about Maciel's crimes, conducted a full investigation into him, but couldn't execute any sentence until 2006 after John Paul had died.

"I want to remember this, because sometimes we forget this hidden work that was the basis of uncovering" the situation, he said.

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