[In the following mixed review, Romney argues that although Traffic is gripping, it fails to achieve a dispassionate feel.]

In the course of his career, Steven Soderbergh has gone from being a well-meaning, low-budget tyro (sex, lies, and videotape) to a mainstream pro-for-hire (Out of Sight, Erin Brockovich), with the occasional blip of personal eccentricity along the way (Kafka, his little-seen absurdist farce Schizopolis, the sublime fish-out-of-water thriller The Limey). Traffic is his most confident film to date, and the sort of grand, serious statement by which a journeyman signals to the world that he would rather be seen as an auteur—a stylist and a pensive commentator on the state of things. And maybe the odd Oscar or Golden Globe wouldn't go amiss.

Well, good for Soderbergh that his boat has come in. He is intelligent; he takes risks; he's interested in exploring structures and visual techniques—he even photographed Traffic himself, giving it a wide range of visual textures, from sheened Californian pastel to harsh, urgent deep blue and parchmenty yellow-brown. It's an impressive exercise; I only wish it seemed to be more heart, more urgency, or that it aspired to reimagine the world, rather than attempted such a detached, quasi-documentary view of it. It is a film with a thesis, in a peculiar sense, for it proposes that, when approaching the issue of drug use and trading in the United States, hard-and-fast theses are neither tenable nor useful.

Written by Stephen Gaghan, the film was inspired by Traffik, the mid-1990s Channel 4 series about the drug trade. It is structured as a panorama of the drug trade in America, suggesting that it infiltrates every corner of life. Soderbergh and Gaghan propose a collection of jigsaw fragments that gradually fit together, almost too conveniently at moments. The characters include a Mexican cop (Benicio Del Toro), his task-force boss (Tomas Milian) and, in the US, the worthy, patrician politico Robert Wakefield (Michael Douglas, whose screen gravitas is just about perfect these days). Wakefield is soon to take on the post of national drug tsar. In Cincinnati, a gang of well-heeled high-school kids sit around sampling coke and smack. In San Diego, a group of ladies who lunch chat about the dangers of cholesterol.

Little by little, the picture builds up. The fresh-faced schoolgirl (Erika Christensen) taking her first steps towards being a junkie is none other than the daughter of the drug tsar. One of the rich women (Catherine Zeta-Jones) discovers her wealthy businessman husband has just been arrested for drug dealing, with connections leading straight back to Mexico. Everyone and everything will tie up one way or another; and while this sort of self-enclosure can be gratifying in more fanciful fictions (in something as playful as Magnolia, say), it is uncomfortable in a film that claims to comment on the real world. It is too crushing an irony that Wakefield's daughter should become a junkie just as he is stepping up to the podium to announce his commitment to the “war on drugs.” That leads to a pointed scene in which he denounces the uselessness of the military metaphor—what can it mean when you end up waging war on your own family members? Too often, the narrative seems engineered specifically so that characters can make points about moral contradictions.

The film is at its best when it dares to be fragmentary and cut corners. At one point, Del Toro's detective is despatched to the US to intercept a dangerous hood. He finds himself getting chummy with his target in a gay bar, but, just as we wonder what will come next, the miscreant is already back in Mexico, under arrest. The secret to these sprawling, thousand-and-one-story structures is that some stories should simply go untold, or merely be hinted at.

That is why the film starts to freeze when we get into the story of Wakefield and his daughter. Suddenly, it's in danger of becoming a problem-of-the-week TV movie, as Wakefield trawls through seedy hotels looking for her. The most awkward moment comes when we are simply read a lesson by an unconvincing embodiment of absolute corruption, a cynical posh boy out of Bret Easton Ellis, who reads Wakefield a street-smart lesson on inner-city economics. Much the same happens when the drug dealer Ruiz (Miguel Ferrer) lectures his captors on the futility of their attempt to control border traffic. “We on Larry King, man?” quips a cop, mercifully puncturing the didactic mood.

Overall, Traffic is rarely that preachy, but has many sensible, liberal points to make. It points out that corruption and compromise are so rooted in the economic system that attempts to target an easily identified and demonised enemy are meaningless and hypocritical. It takes special issue with the warfare metaphor, particularly through the too obviously sinister figure of Milian's General Salazar, who is there to show that military ideology inevitably goes hand in hand with betrayal and senseless attrition.

Nor is this a moralising film, although the moral nature of some characters is too clear-cut for it to be truly analytical. Traffic is gripping because it is, in effect, a melodrama, and a very well-directed and well-acted one. It pretty much avoids the hysteria that usually comes with the subject, but it doesn't quite live up to its intent to be a dispassionate, “state of things” film. But it will give pundits on Larry King and other current affairs shows plenty to chew over—and that, you suspect, was what was intended all along.