The U.S. Department of Justice is asking an appellate court to let Florida enforce its illegal entry and re-entry law.

The case, brought by immigrant advocacy groups, raises questions about whether and how states can police illegal immigration.

The U.S. Supreme Court won’t allow Florida to enforce its undocumented immigrant illegal entry and re-entry law while litigation continues in the case that led to a federal judge finding the state’s top legal officer in contempt of court.