Whatever comprehensive immigration reform plan emerges from Congress will almost certainly make it more difficult for future immigrants to enter the country illegally — and, if they do, will make it harder for them to stay. One of the likely mechanisms of that is the E-Verify hiring database, which is designed to keep illegal immigrants from working in the United States. Since it was introduced, E-Verify has been a deeply flawed system. Now, though, some of its problems are being fixed.

E-Verify determines whether job applicants are legally eligible to work in the United States by checking their names against databases kept by the Social Security Administration and the Department of Homeland Security. Unfortunately, in its early iterations, the system both failed to detect illegal workers more than 50 percent of the time and, in far too many cases, wrongly denied eligible applicants the right to work.

That may be changing. U.S. Citizenship and Immigration Services recently rolled out an updated self-check system called myE-Verify, which allows workers to edit their profiles in the E-Verify database and challenge information they believe to be inaccurate. It includes a component called Self Lock through which individuals can "lock" a Social Security number. If someone tries to get a job using your number, both you and the potential employer will know. Although it is only available in five states and Washington, D.C., this is clearly a step forward.

But it also moves the country closer to a more nuanced set of problems. Five states require employers to use E-Verify, and an additional 13 require that it be consulted for state employees or, in two cases, employees of state contractors. More than half a million employers nationwide use the database, many of them voluntarily. But as the program expands, illegal immigrants who have been here for years and might be eligible for an eventual path to citizenship could lose their jobs and face deportation.