A ban on compasses just isn't going to work. It's too easy to cheat.
A much harder thing to hide was a priest being married (or effectively so) during the time when clerical celibacy was enforced. Since I'm the direct descendant of a priest, the son of a bishop, the son of a priest in those times, I can assure you that my very existence demonstrates the spotty enforcement of THAT ban.
(said bishop was Jon biskup Arason, the last RC bishop of Iceland. In fact, when the messenger from the Danish king arrived saying Iceland was now Lutheran, the other bishop said, "ja, sure, you betcha" and married his woman. My ancestor said, "down with heresy", and marched south to imprison the turncoat. So Iceland stayed RC for one more winter until the sea ice melted and the Danish king could land soldiers. NB: quotes above not exact translations
)