Maybe this counts as a bug? Generally Casus_Belli_Caught and Casus_Belli_Success should be supported for the same actions, I think, though some actions always success and thus there's no _Caught cases.
Current patch has an inverted check causing it to check casus belli only if players are already at war.
Reply To cazfi
Current patch has an inverted check causing it to check casus belli only if players are already at war.
Fixed. Also: If no city or unit on target tile has other kind of owner, treat one with already ongoing war as the main victim.
Successful paradrop actions can give casus belli, but failure never can. It should be supported in the case where paradrop happens to a city.