There is already little enough reason to go to war. We need more war. To arrest a noble of a foreign realm is an act of war. If you arrest a noble you are committing an act of war, which requires you to click the "declare war" button. Pretty simple.
Arresting a foreign noble is not an act of war. I can arrest an infiltrator who tries to steal gold without declaring war.
Furthermore, as I've said, the current system
doesn't create more wars. It creates
less wars, because it raises the
cost of provoking wars. Yes, it raises the benefits of war, but that is far less important than the question of the costs to make the actual transition. And, as noted, it means that only a ruler can do anything about a war (click "declare war") while, if arresting were possible,
anybody could provoke a war.
