Hacked Off: The art show that's driven Banksy up the wall

New Yorkers are flocking to see his works – but the world's most notorious graffiti artist isn't happy. Guy Adams explains why

When is a Banksy not a Banksy?

That is the million, or rather $450,000 question facing bonus-fuelled New York collectors who are beating a path to a new, and unsanctioned, exhibition of work by the world's most famous street artist.

The Keszler Gallery in the Hamptons, Wall Street's favourite holiday destination, is facing stern criticism from Banksy representatives and his fans after attempting to sell two high-profile works of public art, which were originally intended to brighten up the streets of Bethlehem.

The pieces, referred to as Stop & Search and Wet Dog, were stencilled on to prominent walls in the West Bank city during a visit by the British artist in 2007. They disappeared shortly afterwards, only to re-emerge at the Keszler Gallery in Southampton Village late last month.

News of the sale has angered Banksy enthusiasts, who argue that the works were meant for public consumption. They argue that street art is meaningless – and therefore value-less – outside of its original context, and say that foreign art dealers had no right to participate in their removal.

The gallery takes an opposing view. It insists that the pieces, among seven large Banksy works in its new show, were legitimately purchased and exported from the Palestinian territory. If left unprotected in their original location, they were in severe danger of deteriorating, and by now would almost certainly have been vandalised.

Fuelling the controversy is Pest Control, an organisation that is the nearest thing the reclusive British artist has to official representation. In a statement to Artnet magazine, it claimed that only one of the six pieces in the Keszler show had been formally authenticated as Banksy's work, and admonished the gallery for removing them from their original setting.

"We have warned Mr Keszler [the gallery's owner] of the serious implications of selling unauthenticated works, but he seems to not care," read their statement. "We have no doubt that these works will come back to haunt Mr Keszler."

The debate highlights the problems that emerge when the soaring contemporary art market turns what some view as petty vandalism into a prized commodity. These days, Banksy pieces can fetch as much as $1.9m, meaning that his public works are often thought to be worth more than the building they originally graced.

In truth, that often isn't the case: without formal authentication, it is tough to find collectors willing to invest hundreds of thousands of dollars in a work of art. And Pest Control rarely authenticates one of Banksy's public pieces. Robin Barton, the British art dealer who brought the Bethlehem works to the US, told The Independent that he sourced them from a pair of Palestinian entrepreneurs who had removed them from their original location. The duo spent two years trying, and failing, to find a willing buyer. Had he not intervened, they might never have left the West Bank, he says.

"They had tried selling them on eBay, and tried selling them to private clients. But at the end of the day, these works are on five and a half tons of concrete. They are cumbersome and fragile, and difficult to install, and because like most of Banksy's public works they are not formally authenticated, it is very difficult to resell them on the secondary market in the way that you can sell his prints. If we hadn't come along, I don't think they'd have survived."

Stop & Search, which shows a young girl frisking a soldier, was legally purchased by the entrepreneurs from the owner of the butcher's shop in Bethlehem on which the work was left. Wet Dog, which shows the outline of the animal, was removed from a derelict bus stop. He said there is paperwork to support the provenance of both pieces.

Mr Barton denied allegations of profiteering, saying that he had invested a significant sum in transporting the works to the US, and also in having them restored and stabilised, without which they might have fallen into disrepair. Entry to the Kezsler Gallery, an old power station, is free, he added, meaning the public is able to enjoy them.

"There's been a lot of sniping about what we have done. But I have never been involved in the actual removal of Banksy art. I would view that as grave-robbing. What we have done is to take care of works that had already been physically removed." Neither of the pieces, valued at about $450,000, has yet sold, he added.

Mr Barton's partner in the venture, gallery owner Stephan Keszler, added: "In a perfect world, as per the wishes of the artist, the works would always be at their purest when they remain site-specific, but the harsh reality is that very few pieces survive... They would have absolutely been destroyed in Palestine."

Not everyone's convinced, though. "I just find this so sad," said Sebastian Buck, who runs the street art blog Unurth. "Some hedge fund dude is going to be able to buy these things that would otherwise have remained out in public for thousands of people to enjoy. Street art is meant to be viewed in its natural environment, not in a gallery or in some rich guy's house. That's why it's called street art."