......international law allows nations who are attacked [e.g. the state of Israel, 1948, 1967, 1973], to occupy and annex land that was previously recognised as being a part of another state [e.g. Arab states, 1948] because of aggression and attacks, upon a neighbouring state [Israel, 1948].
And international laws does not prohibit a state which was attacked [e.g. the state of Israel, 1948], from occupying and annexing the lands of an aggressor, so as to prevent further attacks.
......"ISRAEL AND INTERNATIONAL LAW....
Israel’s presence in all these areas pending negotiation of new borders is entirely lawful, since Israel entered them lawfully in self-defence. International law forbids acquisition by unlawful force, but not where, as in the case of Israel’s self-defence in 1967, the entry on the territory was lawful. It does not so forbid it,
....
for the effect of such prohibition would be to guarantee to all potential aggressors that, even if their aggression failed, all territory lost in the attempt would be automatically returned to them. Such a rule would be absurd to the point of lunacy. There is no such rule..."
http://www.melaniephillips.com/diary/?p=1528