First off, a terrorist group such as Hamas would probably never bother to use a radiological weapon, because it's not body count that Hamas is after--it's shock value. Katyusha rockets hardly ever hit anything and almost never kill anybody; the reason they're effective is they go KABOOM when they hit something.
What's more shocking than irradiating a large parts of the city, scaring tens of thousands of people? Terrorism, as the name implies, is about using terror to force your enemy to make concessions.
The only thing that could prevent Hamas from using it would be the fear of Israeli crackdown - I mentioned that in my scenario.
And second: while Israel's most violent reprisals have, in the past, provoked a great deal of protest from other nations, they have never resulted in action from other nations. You never see the UN marshalling a peacekeeping force to smack down the Israelis and restore peace.....probably because the UN would get its ass kicked.
Well, most of the loud critics of Israel are just as hypocritical as the Arabs who claim to care about Palestinians, while they only use them as a tool to keep the West under constant pressure.
Do you really think that the British or French governments give a damn about Palestinians? No. They have to pretend so because the biased media and the resultant ignorant anti-Israeli public opinion supplemented with hundreds of thousands of Arab immigrants would give them hell.
Anyway, Israel doesn't need to listen to the EU, because the EU discredited itself by its one-sided policies. We're the biggest provider of aid to the Palies, but our lame leaders have been utterly incapable of using this as a leverage in negotiations with the Palestinians.
You know, negotiations like
"if you don't stop firing missiles, we won't send you a single €uro. Yoiur choice."
Conclusions: an attack with bombs laced with radioactive material is worthless to Hamas, and the end result would be Israel getting away with its dissolution of Gaza, practically scot-free.
Media would play an important role. Since the politicians are cowards in nature, they'd adjust their reaction to the strength of the public opinion on this matter.
I think the initial shock resulting from use of chemical and radiological weapons by Hamas would turn most of people in Europe/US/developed world against Hamas and Palestinians in general.
This would of course change during the Israeli campaign, but it would probably leave Israel with solid enough moral high ground to carry out such a huge operation.
Anyway, the Israel-bashers would then, in few weeks after the end of the operation when the memory of the WMD attack on Tel Aviv would sufficiently fade, renew their anti-Israeli campaign and win the public opinion back with pictures of homeless Palie kids and other crap like that.
