The "set_allow_title_revokation" effect is probably what you're looking for. You can probably just fire an event that does "set allow_title_revokation = no" in an "on_new_holder"-triggered event.
If you don't have conclave, you might want to do that for all viceroyalties in each of the crown authority laws as well - if you change your crown law, you also change your viceroys' crown laws, which might accidentally allow them to revoke titles.