In the recent decision of Chamber of Commerce v. Whiting (5/26/2011) the U.S. Supreme Court upheld an Arizona law that: (1) allows the state to revoke the business licenses of private employers who knowingly or intentionally employ unauthorized aliens; and (2) requires all private employers to use the federal "E-Verify" system to confirm the immigration status of their employees. Following this decision, any other state in the nation may, if it chooses, adopt an employer-licensing law that provides for the same requirements and penalties as the Arizona statute.
The "Legal Arizona Workers Act of 2007" allows Arizona courts to suspend or revoke any necessary business licenses of private employers within Arizona if an employer knowingly or intentionally employs an unauthorized alien. The Act also requires that every private employer, after hiring a new employee, "shall verify the employment eligibility of the employee," using "E-Verify," which is federal internet database maintained by the federal government that allows an employer to receive basic information relating to an employee's work-authorization status. Use of the E-Verify system under federal level is strictly voluntary, as the Secretary of Homeland Security is expressly prohibited from requiring any person or entity outside of the federal government from participating in the E-Verify program.
The U.S. Chamber of Commerce and various other business groups sued various Arizona public officials charged with administering the Legal Arizona Workers Act of 2007, arguing that the law's provisions were both expressly and impliedly preempted by federal immigration law. After examining the statutory text and operations of both the federal immigration law and the Legal Arizona Workers Act, a 5-3 majority of the Court determined that nothing in the federal immigration law prevented Arizona from adopting, implementing and enforcing the Legal Workers Act as it had.
Going forward, the majority's sanction of the provisions of the Legal Arizona Workers Act opens the door for any other state that wishes to adopt the same manner of enforcement scheme, to pass their own statutes that are identical to Arizona's, without concern over whether it is constitutionally permissible to do so. Whether any states will choose to follow suit and create the same type of license-revocation sanction as exists under Arizona law for an employer's knowing and intentional employment of unauthorized aliens, remains to be seen.
You can read the Court's full opinion in Chamber of Commerce v. Whiting here: http://www.supremecourt.gov/opinions/10pdf/09-115.pdf