(FORTUNE Magazine) – How did they get here? Maybe one of them paid some guy a few thousand pesos to guide him across the desert on foot. Another could have folded himself into a box hidden in the bowels of a trucker's rig. None of that matters now, because they've been caught. And here they are, 20 men sitting in a cramped, poorly ventilated cell at the El Paso INS Detention and Deportation Center, tired, jobless, and far from home. The INS officers here speak their language, or some gringo form of it, but they clearly don't understand why these men traverse fences, rivers, and man-made canals, all for the possibility of busing tables at a Howard Johnson's in Fresno--or ending up in a holding pen like this one.

On this hot August day, the thick metal door of the cell swings open and a blue-eyed man with slicked-back hair and a flamboyant moustache strides into the room. "Good morning, gentlemen," he says in perfect Castilian Spanish. "I am Dr. Juan Hernandez. The only bad thing you did was cross the border, and we are working with the U.S. officials to reduce the amount of time it takes to process your cases." Some of the detainees nod. Others give Hernandez quizzical stares. "I also bring you a personal message from your President, Vicente Fox: 'We are waiting for you back in Mexico, trying to create opportunities for you there.'"

Juan Hernandez, the Fox-appointed head of the Office for Mexicans Living Abroad, is on the front lines of a crucial economic debate. Beneath the heady policy arguments and the angry protests about globalization, the very human trend of migration, both documented and undocumented, continues unabated. At this very moment, one in 50 people worldwide is engaged in some kind of international relocation, according to the International Organization for Migration. The U.S. accepts more newcomers than any other nation--typically 1.1 million per year--but that's still less than 2% of the world's migrants and asylum seekers.

Since the Sept. 11 terrorist attacks in New York City and Washington, some politicians have cried out for safer borders, for a slowdown in the pace of immigration. But isolationist forces in the U.S. and other wealthy countries will have a tough time shutting out foreigners. In this global economy, increasing life spans and declining fertility rates are making so-called replacement migration an economic necessity for many countries. A recent United Nations population survey, for instance, projects that Germany, Italy, Japan, Russia, Britain, and Spain will experience population shrinkage and a dramatic increase in the percentage of those over age 65 in the next 50 years. The upshot? A dip in the working-age population, which could translate to a falloff in economic output--unless those nations take in more immigrants. The U.S. has been welcoming enough immigrants each year to maintain current levels of productivity. But the Bureau of Labor Statistics projects that by 2008, the country will have a surplus of more than five million jobs, many of which will require only a high school education and minimal training.

That may seem hard to imagine just now, on the heels of the Nov. 1 announcement that the U.S. unemployment rate has hit a nearly five-year high of 5.4%. But no matter how you measure it, foreign workers--from the Pakistani programmer to the Mexican garment maker--remain vitally important to the U.S. economy. The nation's 27.6 million legal immigrants produced an estimated 10% of U.S. GDP last year; the roughly six million undocumented immigrants accounted for still more. What about the saw that immigrants steal jobs from Americans? A study released in August by UCLA's School of Public Policy and Social Research refutes it. "By taking jobs for which they are better suited, immigrants free up natives, allowing them to be employed in more specialized production," the report notes.

For economists, migration is all about push and pull. Countries with low average wages have high push factors; those with high average wages, and insatiable demand for service-sector employees, have high pull. This economic tug of war defines the relationship between Mexico and the U.S.--the U.S. has all the pull, while the Mexican economy is relentlessly pushing its residents abroad. This dynamic informs all of Juan Hernandez's work. In the past ten years one in three documented new arrivals to the U.S. has come from Mexico. In that time the number of legal U.S. residents of Mexican ancestry grew 53%, to 20.6 million, helping Hispanics surpass blacks as the nation's largest minority group. Another three million to 4.5 million Mexicans are believed to be living north of the border as undocumented workers, making up roughly three-quarters of all illegal immigrants in the U.S. According to the UCLA study, those undocumented Mexicans added $220 billion to U.S. economic output last year. To Juan Hernandez, that gets to the heart of how U.S. immigration policy exploits the push and pull relationship. "The American economy wants [illegal immigrants]. The U.S. is extending a reward to them, the money, the paycheck," he says. "And at the same time it is saying, 'Don't come.' The jobs are here, but then they have to live like criminals in the shadows. That's just not fair."

That Hernandez even has the job he does is evidence of the power of globalization and its effect on developing nations. Last December, Vicente Fox created the Office for Mexicans Living Abroad and appointed as its head not a career politician but Hernandez, a 46-year-old poet and former literature professor. Since then, Hernandez has been barnstorming the U.S., doing everything from selling Silicon Valley CEOs on the notion of opening factories in Mexico to pleading with American governors and mayors to allow state-funded hospitals to treat illegal immigrants. "They built these roads, these undocumented workers, and you won't give them driver's licenses," says Hernandez, who grew up on both sides of the border and has both U.S. and Mexican citizenship. "They've built these schools, and only in Texas will they permit their kids to go to the university. They built our hospitals, they take care of our elderly, and we don't give them health care. There are millions of them right here [in the U.S.] giving us all of these wonderful things that we have."

To Fox, appointing Hernandez was a key step to a more collaborative relationship with the U.S., one that acknowledges the diminishing relevance of physical borders. The Mexican President is a vocal critic of U.S. immigration policy toward Mexico, charging that the U.S. economy's need for Mexican workers leads to an ever-increasing wage disparity between the two countries and stifles Mexico's economic growth potential. He also believes that the North American Free Trade Agreement (NAFTA), which increased the free flow of capital, goods, and services between the U.S. and Mexico, has failed to properly address the flow of labor.

Hernandez's job falls into three broad categories. He's doing whatever he can to help both documented and undocumented Mexicans with problems in the U.S. He's lobbying to build U.S. support for two of Fox's short-term goals: a Mexican guest-worker visa program and an amnesty system for undocumented workers. And he's also trying to encourage U.S. capital investment in poor regions of Mexico--thus diminishing the need Mexicans feel to leave their country. After almost a year in the job, Hernandez makes the U.S. and Mexico sound like cautious lovers, with himself as matchmaker. "It's Mexico that knows what it wants out of the relationship. We don't want to be a distant neighbor," he says. "Seems to me, the U.S. is still trying to figure it out. It's not really sure what it wants."

Improving that relationship is a daunting challenge for a man who has never worked in the business world, and Hernandez has had some setbacks. For one, he has an academic's penchant for talking publicly about ideas that aren't fully formed. Last May, after 14 migrants died attempting to cross the Arizona desert, Hernandez suggested that the Mexican government drop boxed lunch/safety kits, complete with condoms, along the border. The Mexican press played pinata with the idea, dubbing the proposed kits cajas felices (happy boxes). Hernandez quickly backed down.

But he has also posted a couple of key wins. Last winter he negotiated deals with several U.S. banks to reduce the fees they charge Mexicans to wire money back home; migrants who once paid up to $40 for each wire now pay as little as $1.50. Hernandez also identified 90 "micro-regions," high-poverty areas of Mexico that send the most migrants to the U.S., and is searching for padrinos (godfathers) to adopt those regions by investing or setting up businesses there. So far, he has at least one high-profile success: New Jersey textile manufacturer Jaime Lucero has invested some $21 million to open a 1,300-employee manufacturing plant in the state of Puebla, Mexico, where he was born. "Hernandez is not a politician. Because of that, I trust his ideas," says Lucero, who came to the U.S. illegally in 1975 and became a citizen 11 years later.

Though Hernandez swears he has no political ambitions of his own, he carries out the back-slapping work of business and diplomacy with extreme ease. An hour before his tour of the El Paso detention center, he is talking education over breakfast with the mayor of El Paso, Raymond Caballero. The mayor has an idea to allow Mexican universities to set up satellite campuses in El Paso. "Ignorance knows no borders. Why shouldn't it be the same for education?" says Hernandez. "What can we do to help?"

After the meal Hernandez buzzes off to his next stop: the National Center for Employment of the Disabled. About 90% of the nonprofit's employees are Mexican American. Its garment business is so successful that the center has generated enough funds to build a local charter school and a community center. Hernandez would love to see this model of nonprofit activity replicated in poor Mexican regions. He tours the factory, stopping to make small talk with employees. As he leaves, he sings "Happy Birthday" (in Spanish) to Chief Executive Bob Jones and offers him a signed copy of a book he wrote in 1998, Vicente Fox: Dreams, Challenges and Threats. "We have a lot to learn from you," Hernandez tells Jones as he ducks back into his car. "We'll be in touch."

A week later Hernandez is strapped into a small private jet flying over central Mexico with Pablo Salazar, the governor of Chiapas state, and Albert Zapanta, the American president and CEO of the U.S.-Mexico Chamber of Commerce. The three are traveling to Copa de la Sierra, a remote region in the mountains of war-torn Chiapas. Zapanta's group, which includes member corporations like General Motors and Hewlett-Packard, recently agreed to work with Hernandez to identify possible areas for corporate investment in Mexico's poorest regions. What could Chiapas possibly have to offer a big corporation? Without mentioning the specific advantages that the troubled region may hold for a GM or an HP, Hernandez goes into his sales pitch. "The United States is known for taking chances and looking for new frontiers, whether it be in technology or going to the moon," he says. "This is a virgin area. Yes, it's going to be difficult, but the opportunities for those who come right now are going to be immense. The profits are going to be huge." But even with the backing of Fox and an Administration in Washington that's clearly paying attention, Hernandez will need more than vague hyperbole to persuade GM to build a plant in Chiapas.

Hernandez's job has become harder since Sept. 11. The Bush Administration has cracked down on all forms of border security. Still, Hernandez--who just days after the attack was in New York City to help the families of the 17 Mexican citizens reported missing from the World Trade Center--claims that the new atmosphere in the U.S. won't hinder his mission. He even says he favors more stringent enforcement along the U.S.-Mexico fences. Make it tougher for illegal immigration, he believes, and Americans will experience freer trade and a smoother flow of legal border crossing. Stricter enforcement would also help reduce deaths along the border--more than 500 last year.

Besides, says Hernandez, "Events like those on Sept. 11 have a way of strengthening relations between friends." Just days before the attacks, President Bush had seemed receptive to a much-publicized appeal by Vicente Fox for immigration reform, including amnesty for millions of undocumented Mexican workers. The package has been put on the back burner--along with everything not directly related to terrorism--but U.S. Justice Department spokesperson Dan Nelson insists that it is still in play. "Sept. 11 stopped the momentum cold," says Frank Sharry, executive director of the National Immigration Forum. "But it's only the momentum that's dead, not the issue."

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