Tuesday's raids at Swift & Co. packing plants in Greeley and in five other states should serve as a tutorial for federal officials and members of Congress as they tackle immigration in the coming year.

The obvious lesson is that some sort of comprehensive immigration reform is essential, and soon. It's not enough to boost border enforcement and stiffen penalties against employers that hire people who are not authorized to work in this country, though those measures were approved by the outgoing 109th Congress, and we support both.

Legal immigration must be an ingredient in the mix as well. In addition to students, skilled professionals and the seasonal workers who keep farms and resort communities operating smoothly, there's a clear demand for year-round guest workers - foreign nationals who will accept jobs that employers such as Swift may have a hard time filling.

The raids made that demand evident. More than 250 suspected illegal immigrants were arrested at the Greeley plant alone.

Had a guest-worker program or some other path to citizenship been in place, the tragic breakup of workers' families that resulted from the raids might have never come to pass. Some, perhaps many, of those apprehended on Tuesday had lived in the U.S. for years, raising families and bearing children who may themselves be U.S. citizens. A mechanism that lets such workers live productively without fear of removal is crucial.

Next, the raids laid bare a gaping flaw in Washington's system of workplace verification. The government's Basic Pilot program appears all but useless as an immigration enforcement tool.

Basic Pilot verifies whether a Social Security number provided by a potential employee is an active number and not an invented one. Nothing more. Running a number through Basic Pilot would not tell an employer whether that same Social Security number is being used fraudulently by six other applicants - or 60. The program does not connect a Social Security number with a unique job seeker.

This loophole makes it easy for phony document purveyors - and shady employers, for that matter - to bypass verification requirements.

Congress should patch this gap by requiring the Social Security Administration and the Department of Homeland Security to coordinate their efforts.

Speaking of Homeland Security, the defense proffered by Secretary Michael Chertoff for conducting high-profile, TV-friendly raids doesn't wash. Chertoff claimed that the busts targeted identity theft. Nonsense. There were a few big fish and schools of guppies. Fewer than 5 percent of the 1,200-plus people rounded up on Tuesday were charged with criminal violations.

The busts made great video for the 5 o'clock news - and threw hundreds of families into turmoil. They were meant to send a message - to illegal immigrants and to Americans who believe the Bush administration is lax on enforcement - and Chertoff is fooling no one when he claims otherwise.