arcatech parent
The article states that it was NOT forbidden to kill civilians. Or at least, the US considered it justified.
the US considered it justified
s/ the US / "some bureaucratic process within the military"
which is almost certainly politically influenced, as many decisions at this level are
In this case, I don't think the bureaucracy reflects the will of the people
The US has signed treaties according to which it is forbidden and these treaties are additionally so special that they're treated as applying to even non-signatories, the so-called customary international law.