Twilight on the Line: Underworlds and Politics at the U.S.-Mexico Border.

The U.S.-Mexican border, in the words of journalist Sebastian Rotella, is a "magical place" that transforms "migrants into martyrs, intellectuals into cops, cops into social workers, teenage homeboys into jet-set hitmen, gangsters into tycoons, [and] politicians into gangsters."

At the same time, as this account of the border phenomenon demonstrates with power and insight, the line separating the United States from Latin America also serves as a focal point for violence, corruption, and other evils that have hindered the process of democratization in Mexico, and have cast an ominous shadow northward.

Twilight on the Line does not really tell the story of the entire border between the United States and Mexico. It is rather the story of the border near Tijuana, and a vivid portrait of that once sleepy town best known in North America for the appropriation of its name by Herb Alpert's brass ensemble. Today, Tijuana is the second most populous metropolis on the west coast of the Western Hemisphere, a world capital of narcotics trafficking, a transit station for large-scale illegal immigration into the United States, and a window into what Rotella terms the "dark side of the economic integration envisioned by NAFTA."

Tijuana made front-page news in 1994 when an assassin's bullet cut down Mexican presidential candidate Luis Donaldo Colosio as he was campaigning in one of the city's slums. Colosio had received the nomination of the Institutional Revolutionary Party (PRI), which had ruled Mexico for decades and was at last yielding to pressures that were opening up the political process to genuine competition. The PRI nominee was favored to win despite the relaxation of his party's iron grip, and his assassination profoundly shocked Mexico. A lone gunman was captured, but efforts to discover whether other forces were behind the murder have satisfied few Mexicans.

Rotella puts the killing in the context of the emergence of Tijuana as the headquarters of a multibillion-dollar commerce in narcotics, and describes in detail the corrupting influence of the city's drug lords upon local politics, local law enforcement, and ultimately the national political scene.

Tijuana drug dealers were involved in the shooting of Cardinal Juan Jesus Posadas Ocampo of Guadalajara one year before Colosio's murder, an incident that likewise has yet to be explained adequately. A startling aspect of the prelate's death was the participation of members of a San Diego youth gang, who had been hired by a Tijuana narco-syndicate in a grim parody of the free trade promoted by NAFTA, and were sent to Guadalajara ostensibly to assassinate a rival dealer at the city's airport. Some believe that it was not a case of the cardinal being in the wrong place at the wrong time.

The lawlessness endemic to Tijuana complements the massive flow of illegal immigrants across the nearby border. Rotella describes the difficulties that plague efforts to control the human waves crossing into California, as the U.S. Border Patrol captures a fraction of the entrants and returns them to Tijuana, where they regroup and try again. Indeed, the efforts of law-enforcement officials on both sides of the line have often focused more on protecting the immigrants from the physical threats they face from human vultures who would prey on them, from the natural environment, and from high-speed traffic on the I-5 freeway.

The linkage between immigration and the drug trade comes across vividly in Rotella's account, which also points out how cracking down on the illegal crossings can serve to increase the costs of entering the United States and thereby increase the economic incentives for organized crime to become involved.

Perhaps the most touching aspect of Twilight on the Line emerges from Rotella's portraits of Mexican reformers who have labored heroically to overcome the challenges posed by the border. For example, Federico Benitez, who became Tijuana's police chief in 1992, was a lonely crusader who struggled to modernize his force, foster respect for human rights, and combat criminal elements among his own officers as well as within federal and state law-enforcement agencies working in the city. The latter had been seriously corrupted by the narco-traffickers, to the extent that on one occasion a vicious firefight broke out between federal and state agents working for competing gangs.

Jorge Alberto Duarte, the idealistic warden of the state penitentiary in Tijuana, permitted the wives and children of inmates from southern and central Mexico to reside within, granted conjugal visits liberally, fostered dialogue with the prisoners, and even tolerated the existence of a unique intramural society with its own laws and economy. By doing so, he managed to avoid the kind of killing and rioting that has occurred in penitentiaries in Brazil and elsewhere.

Both Benitez and Duarte paid the ultimate price for their earnest efforts. Federal police ambushed and assassinated Benitez on a cross-town expressway, while Duarte fell victim to kidnappers who snatched him in front of his home and shot him as he struggled to escape from their vehicle.

According to Rotella, the border at Tijuana is "the future in the making," where California meets Tijuana and the best and the worst of both societies collide. Although he gives somewhat short shrift to how Southern California (and especially Anglo-dominated San Diego) is reacting to the collision, his portrayal of the Mexican side of the line is deftly drawn, thoroughly disturbing, and constructively provocative.

Joseph A. Page, a professor at the Georgetown University Law Center, is the author of The Brazilians and Peron: A Biography.