After Congress passed NAFTA, six million displaced people (He means Mexicans. -- Ed) came to the US as a result.

In a little over a month, hundreds of thousands, perhaps even millions, of people will fill the streets in city after city, town after town, across the US. This year these May Day marches of immigrant workers will make an important demand on the Obama administration: End the draconian enforcement policies of the Bush administration. Establish a new immigration policy based on human rights and recognition of the crucial economic and social contributions of immigrants to US society.

This year's marches will continue the recovery in the US of the celebration of May Day, recognized in the rest of the world as the day recognizing the contributions and achievements of working people. That recovery started on Monday, May 1, 2006, when over a million people filled the streets of Los Angeles, with hundreds of thousands more in Chicago, New York and cities and towns throughout the United States. Again on May Day in 2007 and 2008, immigrants and their supporters demonstrated and marched, from coast to coast.

One sign found in almost every march said it all: "We are Workers, not Criminals!" Often it was held in the calloused hands of men and women who looked as though they'd just come from work in a factory, cleaning an office building or picking grapes. The sign stated an obvious truth. Millions of people have come to the United States to work, not to break its laws. Some have come with visas, and others without them. But they are all contributors to the society they've found here.

The protests have seemed spontaneous, but they come as a result of years of organizing, educating and agitating - activities that have given immigrants confidence, and at least some organizations the credibility needed to mobilize direct mass action. This movement is the legacy of Bert Corona, immigrant rights pioneer and founder of many national Latino organizations. He trained thousands of immigrant activists, taught the value of political independence, and believed that immigrants themselves must conduct the fight for immigrant rights. Most of the leaders of the radical wing of today's immigrant rights movement were students or disciples of Corona.

In 1986, the Immigration Reform and Control Act made it a crime, for the first time in US history, to hire people without papers. Defenders argued that if people could not legally work they would leave. Life was not so simple.

Undocumented people are part of the communities they live in. They cannot simply go, nor should they. They seek the same goals of equality and opportunity that working people in the US have historically fought to achieve. In addition, for most immigrants, there are no jobs to return to in the countries from which they've come. Rufino Dominguez, a Oaxacan community leader in Fresno, California, says, "The North American Free Trade Agreement (NAFTA) made the price of corn so low that it's not economically possible to plant a crop anymore. We come to the US to work because there's no alternative."

Instead of recognizing this reality, the US government has attempted to make holding a job a criminal act. Some states and local communities, seeing a green light from the Department of Homeland Security, have passed measures that go even further. Last summer, Homeland Security Secretary Michael Chertoff proposed a rule requiring employers to fire any worker who couldn't correct a mismatch between the Social Security number the worker had provided an employer and the SSA database. The regulation assumes those workers have no valid immigration visa, and therefore no valid Social Security number.

With 12 million people living in the US without legal immigration status, the regulation would lead to massive firings, bringing many industries and businesses to a halt. Citizens and legal visa holders would be swept up as well, since the Social Security database is often inaccurate. Under Chertoff, the Bureau of Immigration and Customs Enforcement has conducted sweeping workplace raids, arresting and deporting thousands of workers. Many have been charged with an additional crime - identity theft - because they used a Social Security number belonging to someone else to get a job. Yet, workers using another number actually deposit money into Social Security funds, and will never collect benefits their contributions paid for.

The Arizona legislature has passed a law requiring employers to verify the immigration status of every worker through a federal database called E-Verify, which is even more incomplete and full of errors than Social Security. They must fire workers whose names get flagged. And Mississippi passed a bill making it a felony for an undocumented worker to hold a job, with jail time of 1-10 years, fines of up to $10,000, and no bail for anyone arrested. Employers get immunity.

Many of these punitive measures were incorporated into proposals for "comprehensive immigration reform" that were debated in Congress in 2006 and 2007. The comprehensive bills combined increased enforcement, especially criminalization of work for the undocumented, with huge guest worker programs under which large employers would recruit temporary labor under contract outside the US, bringing workers into the country in a status that would deny them basic rights and social equality. While those proposals failed in Congress, the Bush administration implemented some of their most draconian provisions by executive order and administrative action.

Together, these factors have produced a huge popular response, which has become most visible in the annual marches and demonstrations on May Day. Nativo Lopez, president of both the Mexican American Political Association and the Hermandad Mexicana Latinoamericana, says "the huge number of immigrants and their supporters in the streets found these compromises completely unacceptable. We will only get what we're ready to fight for, but people are ready and willing to fight for the whole enchilada. Washington legislators and lobbyists fear the growth of a new civil rights movement in the streets, because it rejects their compromises and makes demands that go beyond what they have defined as 'politically possible.'"

The marches have put forward an alternative set of demands, which include a real legal status for the 12 million undocumented people in the US, the right to organize to raise wages and gain workplace rights, increased availability of visas that give immigrants some degree of social equality, especially visas based on family reunification, no expansion of guest worker programs, and a guarantee of human rights to immigrants, especially in communities along the US/Mexican border.

At the same time, the price of trying to push people out of the US who've come here for survival is that the vulnerability of undocumented workers will increase. Unscrupulous employers use that vulnerability to deny overtime pay or minimum wage, or fire workers when they protest or organize. Increased vulnerability ultimately results in cheaper labor and fewer rights for everyone. After deporting over 1,000 workers at Swift meatpacking plants, Homeland Security Secretary Chertoff called for linking "effective interior enforcement and a temporary-worker program.'' The government's goal is cheap labor for large employers. Deportations, firings and guest worker programs all make labor cheaper and contribute to a climate of fear and insecurity for all workers.

The May 1 actions highlight the economic importance of immigrant labor. Undocumented workers deserve legal status because of that labor - their inherent contribution to society. The value they create is never called illegal, and no one dreams of taking it away from the employers who profit from it. Yet the people who produce that value are called exactly that - illegal. All workers create value through their labor, but immigrant workers are especially profitable, because they are so often denied many of the union-won benefits accorded to native-born workers. The average undocumented worker has been in the US for five years. By that time, these workers have paid a high price for their lack of legal status, through low wages and lost benefits.

"Undocumented workers deserve immediate legal status, and have already paid for it," Lopez says.

On May 1, the absence of immigrant workers from workplaces, schools and stores demonstrates their power in the national immigration debate and sends a powerful message that they will not be shut out of the debate over their status. They have rescued from anonymity the struggle for the eight-hour day, begun in Chicago over a century ago by the immigrants of yesteryear. They overcame the legacy of the cold war, in which celebrations of May Day were attacked and banned. They are recovering the traditions of all working people for the people of the United States.

David Bacon is a writer and photographer. His new book, "Illegal People - How Globalization Creates Migration and Criminalizes Immigrants," was just published by Beacon Press.