They're breaking the law, aren't they? How can we condone lawlessness? Isn't America based on the rule of law? These are the kind of questions one hears repeatedly in the current debate over illegal immigration in the House and Senate. The questions, and the accompanying indignation, seem to lead inexorably to a conclusion that we should increase the punishments for illegal immigration. But there is basic confusion about immigration law that is driving many Americans to embrace a draconian approach to illegal immigration. It's partly a confusion about the kind of law that immigration law is; but it is also a confusion about the way immigration law works in reality.

Are illegal immigrants breaking the law? The answer to this question isn't quite as simple as it seems. Many laws are based on commonly held moral views about the protection of life and property. People sometimes argue about what constitutes theft or murder, but acknowledging an act as theft or murder is equivalent to condemning it and to prescribing punishment for those who have committed it.

There are other laws, however, that reflect majority opinion about what is good for society, but are defied by large groups or communities within the society. Laws governing sex, drinking, and drugs fit this category. So, too, do laws defining legal and illegal immigration from Mexico. The continuing protests by Latinos and other Americans, including high officials of the Catholic Church, against the House bill that would make crossing the border without papers a felony is a clear indication that many Americans don't believe that the immigration laws are good for society. They might admit that the people they call "undocumented workers" have broken a law, but they would not say they have done anything wrong and should be punished.

That doesn't mean the Bishop of Los Angeles is right and Tom Tancredo is wrong. But it does mean that our immigration laws, like our laws regulating sexual behavior, lack a moral consensus. The fact that illegal immigrants are breaking the law isn't sufficient to justify new punishments against them. The question is whether the laws should be revised rather than enforced.

What do the laws against illegal immigration do? That, again, seems like a question with an obvious answer: They keep out illegal immigrants. But it's not so simple. Laws are adopted in order to achieve certain objectives, but if they ignore the underlying reality they seek to change, they can have perverse effects. Prohibition was intended to foster a sober, industrious law-abiding working class, but by attempting to impose artificial standards on American life, it failed to cut down on drunkenness and led to the growth of organized crime. By ignoring the underlying reality that they are attempting to change, our immigration laws have also failed to achieve their desired effect.

Immigration law was originally adopted to regulate the flow of immigrants who migrated from Europe to become citizens of the United States. The Immigration Act of 1891 referred explicitly to immigrants arriving "by water." There were special laws regulating the importation of Chinese labor into the West Coast in the late-nineteenth and early-twentieth centuries. But the United States did not regulate Mexican immigration in a similar manner. And there was a good reason why it didn't.

The Southwest and California were once part of Mexico. In the mid-nineteenth century, the United States gained these territories, and later states, by conquest. Spanish-speaking Mexicans had always lived in these lands, and over the next century Mexicans would cross the border freely for jobs in the United States. They took seasonal low-wage jobs in agriculture that still paid much higher than comparable jobs in Mexico. Some remained and became citizens, but most returned regularly to Mexico. The lack of border regulation reflected the longstanding relationship between the two neighboring countries. The flow of immigrants from Mexico to the United States was driven by Mexico's relatively lower wages and by the demand in the United States for cheap labor, particularly in agriculture and mining.

When Congress passed the Immigration Act of 1924, it recognized that Mexico was different. The act set restrictive quotas on immigrants by national origin, but these quotas did not apply to Mexico and Latin America. In the 1960s, however, a liberal Congress began passing immigration legislation that failed to acknowledge this special relationship. And the results were disastrous.

The 1965 Immigration and Nationality Act eliminated the Eurocentric quotas of the 1924 act, but in so doing set quotas for Mexican and Latin American immigration that while equal to those from Europe, nonetheless would have, if enforced, drastically reduced the flow of immigrants from South of the border. By ignoring the underlying relationship between Mexico and the United States, the act unwittingly created a new class of criminal: the illegal alien. Over the next 20 years, illegal immigrants from Mexico exceeded legal immigrants by about twenty-to-one.

But the lax enforcement also meant that illegal immigrants continued to move back and forth between Mexico and the United States. According to Beyond Smoke and Mirrors, a study of Mexican immigration by Douglas S. Massey, Jorge Durand, and Nolan J. Malone, 28 million undocumented migrants entered the U.S. from Mexico from 1965 to 1986, but 23.4 million of them returned to Mexico. The underlying relationship was maintained, but the legal categories were changed. That set the stage for current battles over enforcing the immigration laws.

The outcry over illegal immigration inspired Congress to attempt to restrict the flow on the border. It dramatically upped spending on border control in 1986, 1991, and 1996. But the results were perverse. Illegal immigrants continued to pour across the border--now, increasingly, over the less regulated Arizona desert--but fearful that they couldn't get back into the United States if they returned to Mexico, began staying in the United States permanently. So the recent laws not only didn't stop the flow of illegal immigration, they also helped to create a permanent underclass of undocumented workers. The laws changed the reality in the United States--for the worse.

Isn't the solution to enforce the laws against illegal immigrants? Let's concede that it is not good for the United States to have a permanent underclass of undocumented workers. It encourages crime, overburdens social services, and depresses wages. And it is inhumane to deprive people and their children--through fear of exposure--of the most basic protections that Americans enjoy. But what to do about it? Tancredo, Senate Majority Leader Bill Frist, and various rightwing organizations want to eliminate this underclass by imprisoning and then deporting its members. But it's not so simple.

That approach won't work--and, one would hope, will never be tried. The cost in police and prisons would well exceed whatever net costs Americans now pay for social services to illegal immigrants. The process of enforcement--like the process of enforcing Prohibition--would spawn new kinds of criminality, as well as injustice. And most important, it would provoke profound resistance among those who do not believe the laws themselves are good for society--these include large Latino communities and businesses that employ undocumented workers. During the Great Depression, when relatively few Latinos were citizens, whites in Los Angeles could forcibly deport Mexican-Americans to create jobs for other white Americans. Today, the mayor of Los Angeles is a Mexican-American.

Attempts to drive illegal immigrants out by denying them and their children the most basic social services also won't work. These efforts--sometimes termed a strategy of attrition--would have equally perverse results. Already attempted in Arizona and California, such measures don't necessarily reduce the numbers of illegal immigrants, but they do deepen the divisions between them and the rest of the American working class. The underclass increasingly merges with the underworld. And nothing good comes of that.

Should illegal immigration be legalized? It is futile and wrong to try to get rid of the immigrant underclass by eliminating its members. The only way to get rid of this underclass is to change the legal, social, and economic reality that sustains it. To their credit, John McCain and Edward Kennedy have sponsored an immigration bill--The Secure America and Orderly Immigration Act--that begins to do that, and its provisions on undocumented workers were incorporated into Arlen Specter's Comprehensive Immigration Reform Act of 2006, which was voted out of the Judiciary Committee last week.

According to Specter's bill, undocumented workers who resided in the county as of last May could qualify as legal workers for six years if they pay a fine and begin the study of English language and American history. After six years, they could qualify for permanent legal residence and begin applying for citizenship. Kennedy even inserted an amendment in Specter's bill that would keep the wages of temporary workers roughly in line with those of American citizens who have similar jobs. The fine--a sop to those who think the bill rewards criminal behavior--is probably too large, and the bill lacks certain important protections, but it would still transform the situation of an estimated 12 million undocumented workers.

Yet Specter's bill is nonetheless only a stopgap. By allowing 400,000 low-wage guest workers a year and increasing border enforcement, it aims to reduce illegal immigration. But illegal immigration has been running about two million a year. Maybe new kinds of enforcement will cut that number down, but not by that much. As a result, it's likely that even under the Kennedy-McCain bill, a new underclass would emerge soon after Congress had dispatched with the old. Indeed, that is what happened after the 1986 immigration granted amnesty to existing undocumented workers.

But no need to worry. The Senate is not likely to adopt these measures. McCain has already declared that the bill doesn't have the 60 votes necessary for cloture. Instead, Republicans are now discussing a "compromise" that would only provide a path to citizenship for illegal immigrants who have already been in the country for five years. That would probably leave about 5 million illegal immigrants as the basis for the new underclass. And it's unlikely that House negotiators would even approve a bill with a five year restriction. After all, it's amnesty for law-breakers, right?

If Congress wants to eliminate this underclass for good, it is going to have to take measures that go beyond the proposals already on the table. In the short run, it will have to raise the limit on legal immigration higher than 400,000, which will put considerable pressure on unskilled workers in the United States. Some immigration backers insist that these unskilled workers don't bring down wages. They may not do so within existing occupations in which they are already present. But the use of illegal immigration has transformed jobs like meat-packing into poverty-level employment. To limit the downward pressure on wages, states and the federal government would probably have to increase the minimum wage and also strengthen labor law to recognize unions when a majority of workers wants them.

The United States will also have to adopt measures that spur Mexico to create decent-paying jobs for its citizens. The North American Free Trade Agreement fuelled illegal immigration by imperiling subsistence farming in Mexico. (The Central American Free Trade Agreement promises similar results.) What is needed is an approach by Americans to Mexico similar to that which the original Common Market countries took toward less developed Spain, Portugal, and Greece. This would mean development aid and the acceptance of tariffs to protect industries and farms that can't immediately compete with American or Chinese imports. But don't expect Congress or an American administration to contemplate these kinds of measures anytime soon. Instead, expect the immigration debate to continue, the confusion about the basic nature of immigration law to endure, and the number of illegal immigrants to grow.

John B. Judis is a senior editor at The New Republic and a visiting scholar at the Carnegie Endowment for International Peace.