Well the US could do it. Especially with diplomatic pressure I doubt that Israel would attack US planes.

 

Now if and I'm not saying it will happen but if the UN were to impose the no-fly zone who would enforce it?

Why would the US deploy aircraft for it?

For that matter why would France or the UK?

Most of Israels neighbours might not be interested either since if  I recall correctly previous attempts to engage the IAF did not go that well. Saudi Arabia and UAE might have the gear but not the experience so I doubt that they would go for it.

 

So question remains who will impose this no-fly zone if it passes?

 

Completely irrealistic of course, it's just a diplomatic move to force a US veto once again, making further (realistic) arab ligue demands easier.

 

It's also a mean to keep a diplomatic pressure on Israel.

 

Britain and/or France would certainly not engage a war vs Israël just to protect hamas. And certainly not in the air and so close to Israel.

 

In theory (let's be stupid  say diplomacy and geopolitics does not exist...), the only realistic mean for UK or France to put a military pressure on Israel would be a naval embargo with SSN (european SSN especially UK's are better than Israelis SSK, with better trained crews, Israel lacking of ASW frigates and maritime patrol aircrafts).

 

Of course Israel would probably retaliate by closing the Suez canal with air power and it would become nasty...