Whether Iran’s Mahmoud Ahmadinejad visits Ground Zero or not, he has already achieved what he probably set out to do: Even before arriving in NY –where he is now expected on Sunday — he has created enough ruckus so that he features as this year’s belle of the ball at the annual opening of the UN General Assembly.

For Iran’s terror regime, this is the kind of propaganda coup money can’t buy. For a piece of the action, Columbia University has homed in on Iran’s Islamo-fascist regime, as personified by Ahmadinejad, to speak Monday as part of its series entitled “World Leaders Forum” (This is a “leader?” Has anyone at Columbia got a dictionary? How about “tyrant” or “despot” or “strutting terror-sponsoring megalomaniac” –?)

In spirit, at the very least, Ahmadinejad’s roadshow sure looks like a gross abuse of the purpose for which the U.S. waives most normal objections in order to issue visas for special UN events to UN-visiting thugs-of-state.

Surely the idea of allowing even the worst despots to travel within a 25-mile radius of the UN is solely to let them attend the UN debates, not give them carte-blanche to parade around NY angling for propaganda photo-ops; insulting the memories of Americans their terrorist acolytes have already kidnapped, shot, bombed or otherwise murdered; spouting Orwellian sound-bites, and offering opportunities for p.r.-junkies such as Columbia’s President Lee Bollinger to hitch a ride on a performance that only in the universe of “Darkness at Noon” could qualify as “dialogue.”

At the UN, prime enabler of this outrage — since by lights of the UN charter’s stress on respecting freedom and human dignity, Iran’s regime does not even qualify for membership — Secretary-General Ban Ki-Moon has been busy doing … what? He has been ding-donging a peace bell, and opining, as if he had spent the past 30 years living in a flowerbed on Mars, that a visit to Ground Zero might show Ahmadinejad the error of his ways. (No, Mr. Ban. It would be a chance for Ahmadinejad to savor the thought, on camera, of how his nuclear bomb projects will let him make more and bigger craters).

Last year, Hugo Chavez, after his sulphur-sniffing antics on the UN stage, went swanning around New York doling out fuel vouchers. Ahmadinejad at Columbia is about to top this. In theory, these swaggering thugs are supposed to be here not to prance around on American turf, but solely for UN purposes — which is quite bad enough. Before this game of exploitation goes any further, how about U.S. authorities in Washington doing something to re-define the terms of the U.S.- UN deal for Visas-for-Terror-Loving-Tyrants. The best answer would be to evict the UN itself from NY; the second-best solution would be to tell the despots running the world’s worst regimes that they aren’t welcome here no matter what the UN wants; and the third-best (surely this much, at least, could be done) would be to restrict them to the perimeter of the UN itself. It’s a place with plenty of handy bathrooms and sofas, and a dining room where they are already in the habit of stuffing themselves on delicacies their subjects could never afford back home. In many respects, it is their natural home away from home. And if someone like Ahmadinejad wants to step outside those bounds, the place where he ought to be invited to engage in dialogue is Guantanamo Bay.