It's not a difficult conjecture, how the municipality's police would have dealt with him had they apprehended him in the act. In fact, the property clerk division has confiscated one of Banksy's whimsical productions, the graffiti-style balloons that spelled his name on the front of a building in Queens, and the deputy chief has pronounced the latest, if not the final, official opinion on Banksy's endeavors.
According to the New York Times article, "The letters’ estimated value, according to a gallery owner who specializes in Banksy’s work, is between $200,000 and $300,000. But in the view of the Police Department, which has categorized the balloons as 'arrest evidence,' they are somewhat less rarefied, possibly to their peril." It seems that an appreciative pair of amateur art thieves, thinking to liberate the artifacts from their public venue, were (unlike Banksy) apprehended in the act and the balloons removed to police safekeeping.
“I don’t have it as art on the invoice,” said Deputy Chief Jack J. Trabitz, the commanding officer of the property clerk division, which maintains facilities for evidence storage. “We have it as a balloon.”
Deft, perspicacious, unceremonious, entirely to the point. It's the literalism of the official mind, I think, that is the proper, the sharpest and the most efficient instrument with which to deflate Banksy's balloons and to relegate him, tersely and without any agonized ambiguity, to his proper niche in the artistic pantheon, which would be somewhere in the back, by the latrines.
Whether Banksy's balloon is just a balloon in the way that Marcel Duchamp's "Fountain" is just a signed urinal ("R. Mutt"), I am not qualified to answer, though I suspect it's clear which side of the question Deputy Chief Trabitz would come down on. If you're sympathetic to Banksy's whimsies, then you may find the parallel with Duchamp an obvious one. It may be dabatable whether either is (was) an artistic genius. In the official mind, naturally, there is never any debate. To take Banksy's quirky, graffiti-like balloon installation "as a balloon" is to take "Pee Wee's Big Adventure" as a travel documentary.