Sometimes, standing in line outside the Lumière theatre in Cannes, I find myself wondering whatever happened to Liz, the immaculate American executive last seen being hauled over the barricades at the 2008 premiere of Indiana Jones and the Kingdom of the Crystal Skull. One bouncer had her by the shoulders and another had her by the legs, and she had just time to shout despairingly to her colleagues - "They don't know who I am!" - before she vanished over the side to rejoin the hoi-polloi. Liz may well have been a player back in LA, someone not to be messed with. In Cannes, though, she was a near-criminal: a woman in the wrong place at the wrong time, with the wrong badge around her neck. Let Liz stand as an example to us all. In breaking the code of Cannes, she entered a notorious hall of shame that also includes director Lars von Trier (declared persona non grata at last year's event, after saying he "understood Hitler" and was "a Nazi") and all those trigger-happy film buffs who this year dared to post the lineup before the official announcement. "It is disgusting to play with such a thing," fumed festival director Thierry Frémaux in the wake of this leak. There is a code of conduct for Cannes and it must be respected. Those who don't respect the code will never come back to Cannes. The message is clear: obey the code and, yes, you may look upon the face of Indiana Jones. Break it and you will be cast out like Satan. The Cannes film festival, which opens today, basks in its reputation as the world's pre-eminent movie showcase. It is a crucial launchpad for prestige pictures and a thriving business hub, sustained by a bustling film market behind the theatres. And yet these lofty credentials come burnished - and perhaps buttressed - by a self-aggrandising mystique, the sense that this is less a festival than a kind of high church with its own strict moral framework. Or, as the actor Henry Hopper (son of Dennis) told me: "It's 'Come into our temple. But remember that this is our effing temple, man. You better behave yourself.' The critic and film-maker Mark Cousins prefers to view the setup in more regal terms. "France is a republic, obviously," he tells me. So instead of the pomp and circumstance of a monarchy, it crowns its cultural and intellectual life. Cannes, therefore, has something of the court about it, and its director has the hint of Louis XIV. All the same, he says, there is a religious dimension, too. The rituals, the grandeur, the deification, the massing of hordes, the climbing the steps like Santiago de Compostela. Eve Jackson, culture editor at French news site France 24, agrees. She points out that the organisers recently rebuilt the steps outside the Palais (the regally titled conference centre where screenings and press briefings take place). "They made them even steeper," she explains. This was to give the impression that the guests are ascending to movie heaven. Over the coming 10 days, there will be no shortage of dignitaries ascending those steps. Proceedings kick off with the premiere of Wes Anderson's Moonrise Kingdom, a comedy set in the 1960s about a pair of teenage runaways starring Bruce Willis, Bill Murray, Ed Norton and Tilda Swinton. Then it's full-speed ahead to the finish line, with 22 films in the main competition, scores more in the sidebar sections, and hundreds of others consigned to the market out back. Past glories are embodied by a quartet of former Palme d'Or winners: Michael Haneke, Cristian Mungiu, Abbas Kiarostami and Ken Loach, all of whom have work screening in the main competition. Other potential highlights include Jacques Audiard's Rust and Bone, in which Marion Cotillard has her leg chewed off by an orca; and The Hunt, an account of a modern-day witch trial from Festen director Thomas Vinterberg. Lest this seem too rarefied for certain tastes, be assured that US cinema is out in force. Up for examination is The Paperboy, a sweaty Florida-noir starring John Cusack, Zac Efron and Nicole Kidman. Elsewhere, Reese Witherspoon headlines in coming-of-age drama Mud, while the Brazilian director Walter Salles attempts to bring Jack Kerouac's On the Road to the screen with its freeform magic intact. Perhaps most intriguing of all, we have the premiere of Cosmopolis, based on the Don DeLillo novel, directed by David Cronenberg and starring Twilight posterboy Robert Pattinson as a listless billionaire who takes a chauffeur-driven trip across a Manhattan in meltdown. Cannes prides itself on offering (or purporting to offer) the best of the best. While thousands of films are submitted for the festival programme, fewer than 2% are deemed good enough to make the final cut. Steven Gaydos, executive editor at Variety magazine, feels it's this exclusivity that marks the event out from such competitors as Berlin, Toronto or Sundance. "Cannes is the highest profile, most important and best-curated festival on the planet," he says. An industry boss recently told me that to have your film play in any of the sections at Cannes is better than having it play in the top section at any other festival. I have no reason not to believe him. But is there a downside? Undeniably, all this reverence and exclusivity does breed a kind of snobbery. The result is a byzantine system in which delegates are badged according to rank, selected films are winnowed into various categories, and the rest of the world can go hang. Cannes can be a trial for first-time visitors and a nightmare for those on the fringes. Journalists, for example, are split into five castes, separate and unequal, each with a colour-coded card that allows them into certain screenings ahead of others and through doors few others can enter. The topmost white card, or carte blanche, grants access-all-areas and is reserved for high-status critics (our own Peter Bradshaw among them). At the bottom of the heap are yellow cards, for lowly bloggers, freelance photographers and the like. All this is part of a hierarchy that, in the opinion of Scott Macaulay, editor of Filmmaker magazine, is "as rigid as a fascist state." France 24's Eve Jackson says: "Every year I have friends say, 'Oh, you're going to Cannes. Maybe I'll come stay for a few days.' And I think, 'Well, yeah, you can. But one, you won't see me because I'll be working. And two, you won't see anything else, either.' If the public has no access to the film festival, that means they can't see the stars, can't attend the parties and can't see the films. And, of course, all of this makes the film world seem more elitist than ever. Mark Cousins agrees, up to a point. "The downside is international hubris," he says. Even so, given a choice between the "charmed circle" of the Cannes film festival and the market-driven world of the industry at large, he knows which he'd choose. Commerce, in general, disenchants. And money kills the magic of movie-going. So Cannes' reverence involves a great re-enchantment. Variety's Stephen Gaydos also balks at the notion that Cannes is becoming too cosy and calcified. If you want to see real calcification, he says, look at the rest of the business: the big studios pumping out "pre-sold, pre-digested" fodder that asks questions of no one. Compared to that, the festival is positively radical, even inclusive. "Everyone thinks of Cannes as a citadel, a fortress on the hill, utterly unchanging," he says. But what you have to remember is that the festival has to be recreated from the ground up every year. It has to line up sponsors, select films, and liaise with the French government on a national and local level. So Cannes is constantly evolving and renewing itself. It takes a lot of work to stay number one. It's no surprise to find Cousins and Gaydos so reluctant to condemn the festival. Both are members of what Cannes president Gilles Jacob refers to as "the Cannes family": brought into the fold, they are given free run of the Palais. In this way, all those who attend become part of the pageant: honoured guests at an exclusive party where even those who boo at the end of screenings only add to the merriment, since they are seen to be protesting against the films rather than the festival itself. Let the faithful into heaven and keep the sinners locked outside - be they Liz or Lars or the hapless onlookers out on the Croisette.