As the United States reviews its immigration policies, the goal should be to tighten procedures without pinching off the flow of newcomers that adds to the country's economic and cultural vitality.
One area that demands tightening is the granting and tracking of visas. Sixteen of the 19 Sept. 11 hijackers were in the US legally - raising questions about how visas are issued. Two had overstayed their visas. Theoretically, they could have been found.
But as many as 2 million people are currently in the US on expired visas (nearly half the illegal immigrant population). The US Immigration and Naturalization Service (INS) has neither the technology nor the staff to round them up.
Members of Congress are renewing calls to address this situation. Immigration-reform legislation passed five years ago included mandates to keep better track of visa holders. But the magnitude and cost of the task have led to postponements.
Foreign visitors enter the US at some 300 border crossings, sea ports, or airports - at a rate of more than 300 million a year. True, many of those visitors are Canadians making frequent trips across the border for shopping or recreation. Some cities near the northern border, like Detroit, depend on that commerce.
But the 1999 attempted border crossing into Washington State by a would-be terrorist bomber carrying a forged Canadian passport underscored, permanently, the need for sharper vigilance.
The INS needs a major technological boost to make sure foreign visitors are clearly identified and then kept on file electronically. Congress has to steel itself for a big investment.
And it's not just the INS's job. The State Department is understaffed and underfunded to check out people to whom it issues visas overseas. Six of the Sept. 11 terrorists obtained US visas in the Saudi city of Jeddah.
Schools should quickly inform the government when people holding student visas don't show up for classes, despite the bureaucratic burden. The Senate will soon take up bills to toughen student-visa procedures.
Political asylum procedures should be made less vulnerable to being taken advantage of by those with weak claims and possibly ulterior motives. Canada's loosely policed asylum system has let in individuals later tracked to terrorist cells.
European countries, too, are recognizing that tightened asylum and immigration rules are in order, following revelations of Sept. 11 terrorist links or sympathies in their cities.
All this should not mean closing doors to deserving, hard-working immigrants. But there are times when even a nation of immigrants has to check the locks on its doors.