The US DOD (DOW?) interprets the rule rather more broadly....
The US DOD Law of War Manual allows attacks on object that: sustain the enemy's ability to fight economically; generate revenue that funds the war effort; being war-sustaining targets. US doctrine cites: Oil production and export facilities; commodity production funding military operations; financial assets used to pay armed forces. Under the US DOD logic, oil infrastructure funding a state's military budget can be lawful targets.
Which presumably doesn't include girls schools - a war crime then? The blame for the hit has been acknowledged by the US military - shame their leader can't be as honest.