The universal concept of just and justified is not anything more than a hoax. Every person sees justice their own way. The morally right or wrong is a subjective moral opinion. The person who thinks that something is justified may agree or disagree if it is just or not depending if it favors his view or not,
although anything that is helpful to the society in both the short as well as in long run is just and that act should alone be absolutely justified. Anything else depends on the persons that are affected by the act and its nature caters only for that person alone
Just: Consistent with what is morally right; righteous:
Justified: To demonstrate or prove to be just, Right, Or valid:
These definitions are from American Heritage Dictionary.
An example of when something may be justified but not just:
A man runs in off the street and looks agitated and angry. You are home alone and he is walking towards you in what you feel is a threatening manner. Being near a lethal weapon, You use the weapon to kill the person (in order to defend yourself)
It turns out that the person had been running for his life and ran for cover in your house to escape those that were trying to harm him.
It was certainly justified that you killed him. This was a morally valid decision. But it was not just as killing is not a morally right or righteous behavior, Even in self-defense.