Drug-runners smuggle mules across the US border and cook crystal meth in the dark of the Mexican desert in the dead of night. Meanwhile the cartels face conflict on two fronts: a posse of vigilantes patrol the wilds of Arizona to protect their country, and the concerned citizens of the Michoacán region stage an uprising to reclaim control of their towns. If this sounds like the narrative of a hard-hitting crime thriller, that’s because it is; but Cartel Land (2015) is much more than that. A remarkable documentary, this is adrenaline-fuelled reportage at its most dynamic and compelling, exploring the unwieldy power of taking up arms in defiance.

This happens on both sides of the border but director Matthew Heineman begins in the pitch black with a group of cartel members – masked to avoid the fumes of their product – rather candidly acknowledging the terrible repercussions of their actions. Perhaps if they’d had other opportunities and avenues to explore, they wouldn’t be there. This is the first suggestion of a perceived dichotomy being slightly realigned from black and white to monochrome. Although shocking footage later in the picture reaffirms prior assumptions about the cartels, the murky fringes of indistinguishable and overlapping grey moralities is where Heineman’s camera is expertly levelled.

It’s penetrating iris takes in a veritable cornucopia of vigilante activity – from the night-vision sentry duty of self-proclaimed patriots in the southern United States to the Mexican citizens revolting against their criminal oppressors. Heineman sticks perilously close to the action on both counts, getting his narrative hooks into the audience. He uses some night operations with the border patrol to slowly build tension before exploding into a electrifying and terrifying gunfight on the streets of a cartel-dominated town in Mexico. It’s like a handheld sequence from a modern action movie set-piece and has the exact heart-pounding effect as such scenes are intended to. The cinematography is spectacular throughout, Heineman and co-cameraman Matt Porwoll blending mythic silhouettes against glorious sunsets with the rough and ready reality.

And that is what imbues their footage with such incredible energy; Cartel Land may appear to be a neo-Western but it is non-fiction and the danger is undeniably real. This is at its most evident when one of the film’s two focal points – Dr. Jose Manuel Mireles – is almost killed in a mysterious accident. Mireles is the enigmatic centre of the Autodefensas movement, a physician by day and a moustachioed sheriff decked in a cowboy hat in his spare time. He’s contrasted against the American Tim Foley, the militarised head of what the Southern Poverty Law Centre consider an extremist group. But both man lead in what they feel is an absence of government action, and Heineman’s intimate examination lays bare the moral maze of vigilanteism. It’s a vérité thriller that asks difficult questions even as it refuses to proffer easy answers.

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Ben Nicholson | @BRNicholson