News, 'legal' in this context means deriving authority from law. You use 'illegal' in the context of saying there is no legal authority. Israel bases it's claim - one which the UN has never revoked - upon the current - and recent - international law surrounding the 4th Geneva Convention. If that 'law' does not apply then the former state where no law existed might be invoked. Israel has not done so. Under historic precedent Israel would be justified in doing what it wished with it's newly conquered lands. Take your pick news. I for one would rather wrestling with violations of the Geneva Conventions than the right of conquest. Israel has more of less, hewed to the Geneva Convention.
Western-backed Syrian rebels say kill foreign Islamic State (Reuters)
from the article: Gilad Shalit in video: I've been longing for my freedom for a long time