On Monday, the U.S. Supreme Court invalidated most portions of an Arizona state law intended to crack down on illegal immigration, including employment of unauthorized workers. In a 5-3 decision, the Court declared that most of the law's provisions impermissibly interfere with the federal government's constitutional power to control immigration.

For employers, the most important part of this ruling involves the portion of the Arizona law that made it a crime to work in the state without legal authorization. This portion of the law was a follow-up to earlier legal measures threatening employers who employ illegal workers with revocation of their state business licenses. That law was upheld by the Supreme Court as constitutional last year.

In Monday's decision, the Court declared that federal law makes removal of illegal aliens a matter of civil law. By failing to include a criminal penalty against illegal workers as it did with their employers under federal immigration laws, Congress clearly intended penalties against unauthorized persons to remain civil.

This decision may not have much practical effect on efforts to curb employment of illegal persons. However, Arizona and other states that have modeled their laws after the Arizona example will have their efforts to use the criminal process to deal with illegal employment limited to employers, and not the workers themselves.