I would point a legal sticking point in this situation.
One — all priests, regardless of position within the church, of the Catholic church are recognized as citizens of “nation” of the Vatican. As such they are first subject to Vatican law.
Two — As such the Vatican can invoke its status as a sovereign nation to protect its priests.
This is when treaty law becomes a major pain, imo.
So are all imams citizens of the nation of Islam? - assuming there is such a nation.
If so - send them all back to the countries to which they owe their citizenship.
Only a very few officials of the Vatican, here as diplomats in Washington DC enjoy any diplomatic immunity. The priests at your local church have zero legal immunity for crimes they may commit.
What treaty is this?
Priests are subject to the laws of whatever country it is, where they reside. The Catholic Church does not consider them “citizens” although it does consider them to be subject to canon law.
The only priests who have a separate citizenship are those who reside within the Vatican, which is a separate state.