When Pope Benedict XVI resigns at the end of this month, he leaves behind a Church grappling with a global fallout from sex abuse and a personal legacy marred by allegations that he was instrumental in covering up that abuse. For 25 years, Benedict, then known as Cardinal Joseph Ratzinger, headed the Vatican office responsible for investigating claims of sex abuse, but he did not act until he received an explicit order from Pope John Paul II. In 1980, as Archbishop of Munich, Ratzinger approved plans for a priest to move to a different German parish and return to pastoral work only days after the priest began therapy for pedophilia. In 1981, Cardinal Ratzinger became head of the Vatican's Congregation for the Doctrine of the Faith - the office once known as the Inquisition -- making him responsible for upholding church doctrine, and for investigating claims of sexual abuse against clergy. Thousands of letters detailing allegations of abuse were forwarded to Ratzinger's office. A lawsuit filed by the Center for Constitutional Rights on behalf of the Survivors' Network of Those Abused by Priests (SNAP), a victims' rights group, charges that as head of the church body Ratzinger participated in a cover-up of abuse. The suit alleges that investigators of sex abuse cases in several countries found "intentional cover-ups and affirmative steps taken that serve to perpetuate the violence and exacerbate the harm." "Ratzinger, now Pope Benedict XVI, either knew and/or [in] some cases consciously disregarded information that showed subordinates were committing or about to commit such crimes," the complaint says.