[Ghoulish Delight]

Sorry, if you're going to play legal technicality as justification, you still lose. The cease fire they were accused of violating was an agreement with the UN. The terms of that cease fire certainly gave the UN the option of acting on the violation. However, the very body that signed the cease fire and made the rules did not decide that those violations warranted action. Any action by the US due to that cease fire remains illegal.

If someone is convicted of murder with special circumstances in a state with the death penalty, but the jury recommends against the death penalty and the judge agrees, that does not give a police officer the right to kill the defendant on the grounds that he has been convicted of something that might carry the penalty of death. If the decision was no death penalty, then no death penalty.