In the current debate over unauthorized immigration, many policymakers have proposed improvements to the nation’s ability to verify eligibility to work in the United States. Work status laws are primarily directed at closing the back door on illegal immigration by curtailing the employment opportunities that lure unauthorized immigrants into the country. The existing work verification system is thought to be inadequate to deter these unauthorized workers, hard to enforce, and burdensome on employers. Both state and federal authorities have sought to enforce work eligibility rules through new mechanisms, including state and local mandates and a new federal electronic verification system called “E-Verify.” Yet the future of work eligibility verification programs at the state level—and mandatory E-Verify participation at the state and federal levels—remains uncertain. Congressional support of E-Verify has been uneven, and work status legislation has faced continued legal challenges in the courts. The issues before the courts are likely to turn on issues of preemption and will perhaps soon be decided by the United States Supreme Court...