The thing is,
... that you can't effectively police a country not your own. Help them, fine, train them, fine, then leave. The new Afghan government let some trouble makers go, they may have to face them in the future, as they just did with the school bombing. Whether the ones that committed this latest act were some of those released by the new Afghan government of not. Karzhai, Abdul Abdul, et al, have to be there to enforce the law. Of course, such law/s have to be written, read and understood by all Afghans citizens.