Elusive British graffiti artist Banksy appears onscreen, but retains his anonymity, in his documentary Exit Through the Gift Shop. (Mongrel Media)

Exit Through the Gift Shop, the first film by the British graffiti genius Banksy, is as funny and devious as his artwork. What begins ostensibly as a documentary about the street-art movement as seen through the eyes of a quirky amateur videographer morphs into a biting commentary on artistic integrity and today’s money-driven art world.

What begins as a documentary about the street-art movement morphs into a biting commentary on today’s money-driven art world.

The pseudonymous Banksy, playful as ever, appears in the film, while retaining his tenacious anonymity. He’s interviewed with his face buried in the shadows of a hoodie and his voice digitally altered, like someone in a witness protection program.

He’s not the central character in the movie, however. That role belongs to Thierry Guetta, a dumpy, comical, L.A.-based Frenchman with mutton-chop whiskers and an addiction to taping every waking moment of his life. The owner of a successful vintage clothing store, Guetta at first had no purpose to his video hobby. He pointed his camera indiscriminately at anyone and anything, from celebrities like Jay Leno, to his own wife and kids, to traffic lights and toilet bowls. But in 1999, when he returned home to France on a visit, he stumbled upon a subject perfect for his insistent, prowling lens.

Guetta discovered his artist cousin was secretly Space Invader, whose graffiti takes the form of mosaics inspired by the arcade game. When Invader let his relative follow and film him during his nighttime forays into the streets of Paris, he launched Guetta on a new trajectory – befriending and recording the work of prominent graffitists.

Back in L.A., his Invader connection allowed Guetta to hook up with Shepard Fairey, the boyish U.S. artist now best known for his Barack Obama “Hope” poster. Soon, Guetta had penetrated an international inner circle of street artists that included such underground Picassos as Zeus, Swoon, Barry McGee and the Faile collective. He shot them in action and, if anyone asked, he claimed that he was making a documentary.

A good chunk of Exit consists of his raw footage, giving us a glimpse of these urban guerrillas as they clamber up walls, dangle from bridges and outrace security guards in their efforts to spread their art. Finally, Guetta was able to meet Banksy, the star of the street-art world, and get him to agree to be filmed, with one caveat – Guetta couldn’t show the artist’s face.

Guetta’s camera is there when Banksy visits the Israeli West Bank barrier and decorates it with his distinctive stenciled art. He also accompanies Banksy to Disneyland, where the artist surreptitiously plants a blow-up doll of a Guantanamo Bay prisoner in view of the Big Thunder Mountain Railroad ride. Banksy, who has been dubbed the Scarlet Pimpernel of graffitists, slips away before he can be caught. Guetta isn’t so lucky and winds up getting a taste of the theme park’s Mickey Mouse security operations.

By then, we’ve come to find Guetta both amusing and pathetic. He becomes Banksy’s Sancho Panza, a bumbling sidekick, and the artist tolerates him the way a medieval king tolerates a fool. When Guetta at last is forced to come up with that street-art documentary he’s been promising, he slaps together an abomination he calls Life Remote Control. We get a taste of it: an unwatchable hash of images, it looks like it was edited by a chimpanzee on amphetamines. At that point, Banksy suggests an exchange. He’ll sift through Guetta’s mountain of tapes and make a proper film, while Guetta takes Banksy’s advice and concentrates on his own budding street-art career under the handle “Mr. Brainwash.”

"Artist" Thierry Guetta is the ostensible subject of Exit Through the Gift Shop. (Mongrel Media)

Without divulging the film's outrageous climax, let's just say that by the time it's done, we feel a lot less sympathetic toward the clownish Guetta. And that's intentional – Banksy uses the aspirations of Mr. Brainwash to suggest that graffiti, despite its anarchic nature, is bound by the same standards, including esthetics and originality, as more traditional forms of art. He also has a laugh at the expense of a clueless public that will pay top-dollar for crap if they think it’s going to be trendy or valuable.

Although it claims to be a “failed” doc about Banksy, Exit Through the Gift Shop is in fact a pretty good introduction to the artist’s career and work. Banksy uses Guetta’s colourful story as a front, behind which his own tale is obliquely told. With deadpan narration by Welsh actor Rhys Ifans and a stirring anthem by Richard Hawley (Tonight These Streets Are Ours ), the film also functions as a celebration of the sheer adrenalin-fuelled audacity of all graffitists. Thanks to YouTube, blogs, social networks and other internet tools, we're seeing an explosion in self-expression like never before – but that's all within the confines of cyberspace. There's something bracingly old-school about the idea of sneaking out under the cover of darkness armed with a spray can and risking limb and law to transform blank walls into a gallery for your art.

True, sometimes graffiti is just dumb, ugly vandalism. At its best, though, it is a symbol of the unquenchable, unstoppable creative urge. It turns the streets into one great, democratic, open-air museum – one in which we never have to exit through the gift shop.

Exit Through the Gift Shop opens in Montreal, Toronto and Vancouver on Friday, May 7.

Martin Morrow writes about the arts for CBC News.