Nothing exposes the flaws in a bad law quicker than vigorous enforcement.
That axiom makes a proposal that would prevent farmers from hiring illegal immigrants intriguing -- and frightening.
It's hard to imagine that the stalemate about immigration reform could survive the mess that would ensue. But the staggering economic cost is too high a price to pay.
U.S. ag sales topped $297 billion in 2007, according the Department of Agriculture. Any hit to the industry would ripple through the nation's already shaky economy.
And the agriculture industry predicts much more than a hit. Officials see disaster if Congress goes ahead with a plan to require all employers to run their workers through the E-Verify system.
The software, while not perfect, is far better than current practices for determining whether an employee is legally entitled to work in the U.S.
In the farm industry, current practices amount to a wink and a nod. Workers must produce a Social Security card, but everyone recognizes that forgeries are readily available.
Farmers fear any excess scrutiny of a worker's documentation could lead to discrimination complaints. Of course, the industry's dependence on large numbers of low-paid, temporary workers is an even bigger disincentive to look too closely.
It's hard to calculate the financial damage that strict enforcement of U.S. immigration laws would bring to farm country.
An estimated 80 percent of all field workers are illegal immigrants. Without them, much of the nation's crops simply wouldn't get harvested.
Even in the Great Recession, most Americans aren't willing to take the place of migrant farm workers. Last year, the United Farm Workers ran a "Take Our Jobs" campaign to connect legal workers with ag jobs.
The effort drew about 86,000 inquiries, but only 11 workers actually took the farm jobs offered. The numbers confirm what farmers already know -- their businesses can't survive without illegal workers.
Agriculture Secretary Tom Vilsak and the Farm Bureau Federation President Bob Stallman recently called a news conference to express their concerns about the E-Verify.
If it is successful in weeding out illegal workers, the system would mean economic catastrophe for American farmers, they said.
With food prices already on the rise, consumers could expect to share in the misery.
E-Verify probably is an empty threat. Congress isn't likely to risk the consequences. But let's hope the debate brings us a step closer to immigration reform.
When the law can't be enforced without bringing disaster to a major industry, it's time for a new law.