There's nothing 'legal' about a country invading another and then annexing bits of to suit themselves. It used to be like that but these days the rest of the world gets upset about it. They think if one can get away with then so can anyone else. Besides, it might just be that the next time Israel goes to war it might find it is biting off far more than it can chew.
Suspected Islamist militants attack Mali UN base, several dead (Reuters)
from the article: MESS Report / Nobody wants war, but Israel-Lebanon border is heating up