I was always amazed, growing up near the border in San Diego, at what a difference an imaginary line could make. On one side of the border there was prosperity, economic growth, a robust middle class. On the other side: poverty, corruption, a huge gap between the rich and poor.

That disturbing contrast led me to imagine a world without borders, where everyone enjoyed the economic freedom and opportunity we take for granted in the United States. A world where the individual, not the state, reigns supreme. Such a place remains my ideal.

But that is not the world we live in today, nor will we, anytime soon. We have nations and borders that divide us, and rules for immigration and citizenship. And as long as we do, it makes sense to enforce and follow them. Otherwise we get chaos.

Now President Bush has proposed a new immigration policy that would provide legal status to illegal immigrants working in the United States and to workers from other countries who can show they have a job offer here.

Bush deserves credit for at least addressing the problem of illegal immigration, which has been ignored for too long by a series of presidents. But his proposal is far too broad, and would probably do little to slow the flow of illegals. It might even make things worse.

Already, border agents are reporting a new wave of illegal immigration triggered by Bush's proposal. The president's plan was widely publicized in Mexico and led people to believe that if they could just get into the United States, they would get amnesty when the new rules took effect. That's similar to what happened after the last time the U.S. granted amnesty to illegal immigrants, in 1986. Every time the government does so, it makes fools of those who wait their turn to immigrate legally and creates a strong magnet for people to get here any way they can.

In addition, America's earlier experience with guest worker programs, and that of Europe, suggests that immigrants who enter the country as guests, even with a tie to an employer, often don't leave when their job ends. Such a program can be simply another way to reside here illegally, without having to pay a "coyote" and risk dangerous conditions sneaking across the border.

But the deeper question is whether the United States needs a guest worker program at all, and who would gain and lose from it.

It would certainly help impoverished Mexicans, who would find it easier to come here in search of a better life. It would help American business owners looking for cheap labor. But it would be a major blow to U.S. citizens and legal immigrants at the low end of the of job market, whose wages are bid down by the presence of a large and seemingly inexhaustible pool of unskilled labor.

California's widening gap between rich and poor is already evidence that the state is having trouble absorbing the number of immigrants it has today. The last census found that 26 percent of state residents are foreign-born, the highest proportion since 1890. In four California cities - Glendale, El Monte, Santa Ana and Daly City - the majority of the population was born in another country.

And recent figures show that foreign-born immigrants, legal or illegal, are three times more likely to live in poverty as whites and Asians who were born in the United States, and a about a third more likely to live in poverty as native-born Hispanics and African Americans.

The most compelling argument for liberalizing immigration is that immigrants fill jobs Americans don't want. But to the extent that is true, it's only true because those jobs don't pay enough to attract American labor. Without the safety-valve of immigrant labor, wages would rise until they were high enough to draw workers from other fields.

In some industries, this might cause problems. Garment factories in Southern California that rely almost entirely on immigrant labor might not be able to compete in the world economy paying higher wages. Agriculture, with its seasonal and migrant work in remote locations, probably will always have trouble finding workers, and might need to be treated as a special case.

But surely our economy could survive if the hotels, restaurants, landscapers and construction companies that now employ illegal immigrants were instead forced to hire legal residents and citizens. We would all pay a little more for those services, but we would also have lower unemployment and fewer of the social costs associated with poverty.

Bush's proposal appears to have been an attempt to attract the Hispanic vote. If so, it was misguided. Hispanics who are already citizens are not likely to support a policy that promises to further impoverish them.