(CN) - Pope Benedict's retirement plans may open him up to prosecution by the International Criminal Court for sheltering child abusers, an advocacy group said Monday.

Citing his frail health on Monday, Pope Benedict XVI announced that he will step down as pope after less than eight years in office. He is the first pope to retire in the last 600 years.

Though a surprise to many, one group that the announcement failed to rattle is the Survivors Network of those Abused by Priests (SNAP). It announced hours later: "whether he is in office or not makes no difference, but it may lower the bar of resistance enough for justice to be served."

"In this case, all roads really do lead to Rome," the group said in a statement. "Not only does Pope Benedict XVI bear responsibility in his official capacity for the church-wide policy of systematic and widespread concealment and enabling of the crimes, but he bears individual responsibility in a number of cases in which he ensured that perpetrators would be shielded and protected and left in place to assault more victims."

That group and the Center for Constitutional Rights (CCR) are plaintiffs in a 2011 complaint with the International Criminal Court that accuses Vatican officials, including Pope Benedict, of tolerating and concealing widespread rape and sexual abuse of children around the world.

The complaint included more than 20,000 pages of supplemental materials, including reports, policy papers and government and judicial inquiries.

In his previous capacity as Cardinal Joseph Ratzinger, the pope allegedly centralized the investigation of all cases of clerical sexual abuse in Rome. The church allegedly hushed up accusations of abuse, and "shuffled" accused priests to remote locations where they found new victims.

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