This May Day, we need to stop making work a crime for undocumented immigrants.

In the big immigrant marches that swept the country on May Day in 2006 and 2007, one sign said it all: "We are Workers, not Criminals!"

The sign stated an obvious truth. Millions of people have come to this country to work, not to break its laws. Some have come with visas, and others without them. But they are contributors to the society they've found here, not people who mean it harm.

Again this May Day, immigrant workers will be filling the streets, making the same profound point.

Yet today, the federal government is taking actions that make holding a job a criminal act. Last summer, Homeland Secretary Michael Chertoff proposed a rule requiring employers to fire any worker who couldn't correct a mismatch between the Social Security number they provided their employer, and the Social Security Administration database, assuming those workers have no valid immigration visa.

With 12 million people living in the United States 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.

Some states and local communities, seeing a green light from Chertoff, are passing measures that go even further.

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 one to ten years, fines of up to $10,000 and no bail for anyone arrested.

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

But undocumented people are part of the communities they live in. They will not simply go, nor should they. They seek the same goals of equality and opportunity that everyone else in our country believes in, too.

For most, there are no jobs to return to in the countries from which they've come.

"The North American Free Trade Agreement made the price of corn so low that it's not economically possible to plant a crop anymore," says Rufino Dominguez, a community leader from Oaxaca. "We come to the U.S. to work because there's no alternative."

If Congress stops passing new free trade agreements, and instead faces up to the damage NAFTA and other pro-corporate measures did in Mexico, that would eventually begin to reverse the poverty and desperation that fuel migration.

Trying to push people out of the United States who've come here for survival simply won't work.

And the price of trying not only increases the vulnerability of undocumented workers. It also depresses wages and working conditions across the board.

Unscrupulous employers use that vulnerability to deny undocumented workers the minimum wage or overtime, and to fire workers when they protest or organize. This depresses the wages and rights of workers in general.

Chertoff calls for linking "effective interior enforcement and a temporary-worker program.'' But deportations, firings and guest worker programs all make labor cheaper and union organizing harder.

Instead of making work a crime and treating immigrants as criminals, we need equality, security jobs and rights for everyone.

David Bacon is a California writer and photographer, and author of the forthcoming "Illegal People — How Globalization Creates Migration and Criminalizes Immigrants." (Beacon Press, September 2008) He can be reached at pmproj@progressive.org.