I've signed, but I doubt they could ever make this happen, for all the reasons already given above. It would be political suicide.
Republicans are not the only gun owners - democrats own guns too. And while there is a discrepancy on the types of firearms that should be allowable, there is only minor contention regarding owning any firearms at all - so the supporters of this sweeping treaty would be as rare as vegetarians.
Besides all of that, the writers of this arefundamentally mistaken. I would personally like to see every capable homo-sapien, regardless of country, religion, or whatever, armed to the teeth. That's the treay I would stand behind.
That would be the singular most effective path to a lasting world peace, since it would have the same effect as removing all weapons from the planet - which is impossible - arming every capable human with maximum firepower would even the playing field the exact same way.
Just to be clear what camp I'm in
Nature is bloody in tooth and claw, and we didn't rise above it with harsh language. The only real peace is peace backed-up by the mutual respect of deadly force.