At the climax of Giuseppe Tornatore's shameless tearjerker Cinema Paradiso, the main character returns to his childhood home and finds a reel of film that the large-hearted projectionist (Philippe Noiret) has left for him. It turns out to be a lusty montage of famous kisses, culled from decades of films that the town priest had deemed unsuitable for the public. When the man, now a director, sees all that had been discarded by the priest's censorship, he falls in love with the movies all over again.

Kirby Dick's expose of the workings of the MPAA ratings board offers a similar opportunity. Dick's montages of offending scenes tend to be more frank than those seen in Cinema Paradiso (Natasha Lyonne masturbating, Michael Douglas performing cunnilingus, Hilary Swank pleasuring Chloe Sevigny), and the result is more infuriating than sentimental. But like Tornatore, Dick lifts the veil of censorship, shows what has been deemed indicent, and exposes those who dictate what the rest of us are allowed to see.

At first glance, the MPAA ratings board may seem harmless, nothing more than an innocuous group that provides helpful guidelines to parents about which movies are appropriate for their children. With the help of a suitably angry but nonetheless entertaining parade of talking heads (including Allison Anders, Kevin Smith, Trey Parker, Kimberly Peirce, John Waters, Mary Harron, and Maria Bello), Dick outlines a number of fundamental problems. Unaccountable and unelected, the ratings board is a studio-funded body, and its membership is a carefully guarded secret. And yet, their power is enormous. The difference between ratings translates into millions at the box office, and the damning NC-17 can spell disaster for a film.

In several delicious montages, This Film counts thrusts and beheadings, compares ratings between similar sex acts in different films, and thus reveals the board's biases. Sex is much more restricted than violence, especially if it shows female pleasure, homosexuality, or anything that deviates from the tasteful moving-torsos-under-the-sheets cliché. For instance, Jamie Babbit's teenage comedy But I'm a Cheerleader, no more explicit than the R-rated American Pie, was slapped with an NC-17 rating--apparently for no other reason than that it dealt with a lesbian main character.

With the help of hired private detectives who give the film a compelling subplot, Dick uncovers the identities of the board members. It turns out that the MPAA ratings board doesn't represent anybody in particular and doesn't adhere to any specific guidelines--but it reflexively prefers blood to sperm, straight to gay, studio productions to independents, and Walt Disney to John Waters. In a final twist, the film documents its own struggle with the board, and it becomes obvious that the appeals process is dominated by buyers for the country's largest theater chains, with two church leaders thown in for good measure.

It would be hyperbole to call This Film is Not Yet Rated the most important documentary you'll see this year (An Inconvenient Truth, The Road to Guantanamo, and When the Levees Broke all vie for that distinction)--but it's close. An industry-owned censorship board is obviously unacceptable in a democratic society. The system that gives an unaccountable group of individuals a stranglehood on what Americans see is in desperate need of overhaul. This Film is Not Yet Rated makes its argument with compulsively watchable vigor and wit.