A simple but very realistic fact, not recorded in any "international laws" of yours., Johnny. As soon as Hamas re-energizes from the beating and gets replenished, it will provoke Israel again. Every time it hopes to nflict the greater damage to Israel. And if they get the more potent supply, eventually they may strike a nerve. Even if they reach it only once, that would be enough. This formula of inevitability is as clear as the most clearest thing in the world. If I know it, much more so the Israeli government and the people in the know and suppose to know, know it. So do all the notorious Israel "lovers", deep down wishing some kind of harm done to Israel for variety of reasons. They just prefer to hide behind "what rights does Osrael have". The right to protect herself and her people. Given that it is not only assumed inevitability but Israel's sworn enemies are not even bothering to hide this fact. As a matter of fact they are loudly promoting it. Your "and this right derives from what exactly" is an empty legal coverup, too lame and outdated after what had jsut happened, Johnny.
Police disperse hundreds in brawl in Kafr Manda, northern Israel (Haaretz)