THERE are two approaches to illegal immigration currently being debated in Congress. One, supported by the House, emphasizes border control and law enforcement, including a wall along the Mexican border and increased border patrols. The other, which is supported by the Bush administration and has been passed by the Senate, relies on employers to police the workplace. Both proposals have serious flaws.

As opponents of the House plan have rightly pointed out, walls rarely work; illegal immigrants will get around them one way or another. Unless we erect something akin to the Berlin Wall, which would cost billions to build and police, a barrier on the border would be monitored by largely symbolic patrols and easily evaded.

The Senate approach is more realistic but it, too, has problems. It creates a temporary worker program but requires employers first to attempt to recruit American workers to fill job openings. It allows for more border fencing, but makes no effort to disguise the basic futility of the enterprise. Instead, it calls on employers to enforce immigration laws in the workplace, a plan that can only succeed through the creation and distribution of a costly national identification card.

A national ID card raises serious questions about civil liberties, but they are not the sole concern. The cost estimates for producing and distributing a counterfeit-proof card for the roughly 150 million people currently in the labor force — and the millions more who will seek work in the near future — extend into the billions of dollars. Employers would have to verify the identity of every American worker, otherwise the program would be as unreliable as the one in place now. Anyone erroneously denied a card in this bureaucratic labyrinth would be unemployable.