My approach to this is a little different.
In my business rule layer I check to make sure the FK relationships are good before saving the item.
your business rule should present a user understandable error to the user.
Also in the case of deletes I would also check to make sure the item can be deleted before trying the delete. I would also present a user understandable error.
Rodman
Rod Paddock
Editor in Chief CoDe Magazine
President Dash Point Software, Inc.
VP Red Matrix Technologies,Inc.