In a federal pre-enforcement suit challenging the Legal Arizona Workers Act, which, in certain circumstances, revoke the licenses of state employers that knowingly or intentionally employ unauthorized aliens and requires all Arizona employers to use E-Verify, judgment of the appeals court is affirmed where the plain language of the Immigration Reform and Control Act's (IRCA) preemption clause did not invalidate Arizona's law because the law did no more than impose licensing conditions on businesses operating within the State; nor was the state law preempted with respect to E-Verify because although Congress made the program voluntary at the national level, it expressed no intent to prevent States from mandating participation.