All cases against clerics, both civil and criminal,
must be brought into the ecclesiastical court, unless for
some countries other provisions have been made.
Cardinals, Legates of the Holy See, bishops, even titu
lar ones, abbots and prelates nullius, the supreme heads of
religious bodies approved by Rome, the major officials of
the Roman Curia in reference to business belonging to their
office, cannot be sued in the secular courts without permis
sion of the Holy See. All others, clerics and religious, who
enjoy the privilege of the forum, cannot be sued in a civil
court without permission of the Ordinary of the place where
the case is to be tried. The Ordinary, however, should not
refuse such permission, if the suitor be a lay person, espe
cially after his attempts to effect an agreement have failed.
If clerics are sued in the civil court by one who has not
obtained the permission, they may appear in court because
they are forced to obey the summons if they want to protect
themselves against more trouble, but they shall inform the
Ordinary from whom permission should have been obtained.
(Canon 120.)
So.....it appears that under normal circuмstances permission is required from either the "Holy See" (aka the pope) or the Ordinary (aka the Diocesan Bishop). Exactly how would that work during those not-so-normal times?