I don't crusade much, but I wonder if excommunication status could affect how willing Catholics are to let your crusade through. I could see that working one of two ways.

1: An excommunicated ruler might not be counted as "non-Catholic" for this purpose and not let your crusade through.

2: If a ruler sends a crusade and then gets excommunicated, perhaps good Catholic rulers will view his crusade as a bogus crusade commanded by heretics, and oppose it.

Does anyone know if crusading works that way?