Hi,
Thanks for your question. Not even Ixlana's Binding can keep Squee away. The first thing you do when you cast a spell is move it from where you're casting it (in this case, from exile) to the stack. Then, during 601.2e, we check to see if we're able to cast the spell. Since Squee is on the stack, not in exile, the Binding isn't preventing you from casting Squee, so you would be able to cast the exiled Squee.
EDIT: To put this another way: if your opponent has a Void Winnower in play, and you want to cast Rolling Thunder, you can, since we don't check the converted mana cost until 601.2e. This is a similiar situation. We start casting Squee, which involves moving it from exile to the stack. Once we get to 2e, there's nothing exiled by the Binding (since Squee is on the stack), so the Binding doesn't do anything and you can cast Squee.
Thanks,
Nathan Long
Magic Rules NetRep
Edited Nathan Long (April 19, 2018 06:53:14 PM)