"It is a sin that shames us," Pope Francis wrote. "Persons responsible for the protection of those children destroyed their dignity."

Each of the participants carried wooden crosses bearing the names of victims.

Some see the end of the registry as a way to make it difficult for an incoming Donald Trump administration to target Muslims through such a program.

The imbalance in the world, one Jesuit expert has said, reflects how years of papal pleas and Vatican mandates have not been received or implemented consistently everywhere.