I don't think so. At least not in the manner he did.
Without the UN mandate I don't believe there is a coalition, at least not as much of one. (Who knows, maybe England would go along.)
OK, but I think it needs to be said that final coalition of the willing included no major industrialized nation outside of Britain, Australia and Poland, with Australia and Poland offering no real support in troops or treasure beyond token gestures. It was the U.S. and Britain. I'm not sure how the major UN powers at the time (Germany, France, China, Russia, India, etc.) could have shown more of a repudiation of Iraq, since we're talking UN mandates. Yet the Bush administration still decided to forge ahead. It's not inconceivable they would have done whatever they felt like doing. Knowing that, it's not a good excuse to say Bush couldn't stay in Iraq because of a UN mandate. Come on.
But I don't see any kind of long occupation like we did without that UN mandate. Yeah, he might've bombed them, but I'm kinda doubtful of any kind of troop invasion, and certainly not one that was long and drawn out. And I definitely don't see us creating any type of provisional government or engaging in nation building. Without UN approval it's just not going to happen IMO.
Fern
Yeah, again, I think you're naive if you think the Bush administration wouldn't have engaged in the Iraq war without a UN mandate. I just don't see any evidence that the Bush admin cared one way or another.