HOW MANY border guards would it take to make the U.S.-Mexican border impenetrable? The answer -- like the answer to an older question, "How many policemen would it take to enforce Prohibition?" -- is: It depends. It depends on how much money people are willing to spend and how many trappings of a police state they're willing to accept. With billions of dollars more invested in electric fences, guns, workplace raids, roadblocks and national identity cards, illegal immigration could be slowed, though not halted, under current immigration laws.
On the other hand, if those underlying laws were altered to reflect economic reality -- that people cross the border because American employers want to hire them and that they will continue to do so as long as there are jobs -- then stricter enforcement might succeed. Grant temporary visas that allow workers to come and go; permit those who are here to regularize their status after paying taxes and a fine, learning English, and waiting their turn; improve the immigration bureaucracy to cope with larger numbers of visa and green-card applications. Then stricter border controls would have a chance.
Does President Bush understand that equation? In his speech last night, he dwelled first on enforcement, the preferred tactic of the grass roots of his party. He called, reasonably, for better technology, tamper-proof identity cards for legal immigrants, more rapid deportation of captured illegal immigrants and more funding for local officials. Less reasonably, he also promised to deploy the National Guard, which he already has overtaxed and under-supported.
But for the first time in such a setting, the president stated eloquently that enforcement is not sufficient. He insisted on "comprehensive" reform, which he said must include a temporary visa program and a route to legality for the undocumented immigrants who are here -- what he called a "rational middle ground" between amnesty and deportation. This matters: At the moment there is an immigration bill on the Senate floor that contains some of the elements needed for a qualitative change in U.S. immigration policy. But the House has passed a bill that would effectively criminalize all of the estimated 12 million illegal immigrants in this country, while offering none of the reforms needed to make enforcement work.
Mr. Bush will have to push hard to achieve legislation closer to the Senate vision. He responded weakly when the House passed its draconian measure; he may not have the political strength now to resist it. But last night was a good start. "Our new immigrants are just what they've always been: people willing to risk everything for the dream of freedom," the president said. "We honor the heritage of all who come here, no matter where they come from, because we trust in our country's genius for making us all Americans, one nation under God." Well said; now the president will have to persuade his party to share in that trust.