Mark linked to this earlier. I particularly liked this bit:

Fewer jobs and genuine border control ought to curb illegal immigration. Good. Naturally, there’s another point of view. It is that the United States needs more unskilled workers to fill jobs native-born Americans won’t take. One solution is to admit more unskilled workers legally. By this view, Hispanics are assimilating economically and culturally as fast as some groups in the past.
Perhaps. But common sense and available evidence suggest skepticism. If there are “shortages” of unskilled American workers, the obvious remedy is to raise their wages. A Texas roofing contractor testified to Congress that he couldn’t get enough roofers at $9 an hour. OK, increase it to $10 or $12. Higher wages will bring forth more workers. Perish the thought. Business groups, led by the U.S. Chamber of Commerce, clamor for more “guest workers.” That’s a euphemism for cheap labor. These business groups seem unperturbed by extravagant increases in CEO pay. But they’re horrified by anything that might raise the wages of maids, waitresses, laborers or gardeners.
As for assimilation, it’s true that millions of Hispanic families are moving into — and reshaping — the American mainstream. But average trends look less encouraging. Since 1990, about 90 percent of the increase in people living below the government’s poverty lines are Hispanic. That has to be mainly immigrants and their American-born children. The median net worth of Hispanic households is about 9 percent of that of non-Hispanic whites (net worth is what people own minus what they owe), reports the Pew Hispanic Center.
Assimilation takes time. The big difference between today’s Hispanic inflows and past immigration waves is that those stopped. History or restrictive laws intervened. There was time for newcomers to adapt. Left alone, there’s no obvious reason why the present Hispanic immigration should even pause. Today’s unskilled arrivals make it harder for yesterday’s to get ahead. The two compete.
There’s a paradox. To make immigration succeed, we need to curb some immigration. That’s why it’s vital to control our border. It also explains why it’s important not to “solve” that problem merely by legalizing these huge inflows.

The intellectual tide continues to move the pro-enforcement way on this issue.