You mean legally part of Israel from Israel’s perspective, right? AFAIK neither the west bank nor the gaza strip are recognized as legitimate territories of Israel under international law but I admittedly know very little about international law :)
Israel explicitly rejects Gaza is part of Israel. Some Israeli politicians might claim otherwise, but the government policy has been to refuse claims it is since '67, and to now insist it's not even under occupation.
In international relations, possession by a nuclear power is 10/10ths of the law.