Different invasion rules for countries with real governments and thos without. You really can hold a govt responsible for its actions - if that govt has effective control of (most of) its sovreign territory, eg Panama or Iraq. But if there is no real govt - Somalia and Afghanistan in 2001 - then you are playing by different rules. Deterrance is a real policy when there is a govt - it is indeed an option for say Iran. But deterrance is not an option for an Afghanistan or a Somalia.

Cheers

JohnT