The U.S. Supreme Court upheld an Arizona law requiring employers to use the federal E-Verify system.
Here is an analysis from SCOTUS Blog:
A divided Supreme Court on Thursday sent a strong signal that states will be free to experiment with new laws dealing with unlawful aliens living within their borders, at least when the states seek to control access to jobs. The usual argument that immigration policy has to be uniform, across the nation, would appear to have a significant loophole. Whether the new 5-3 ruling upholding the less controversial of Arizona’s recent legislative attack on immigrants will actually reach further than jobs, affecting other state and local initiatives, is likely to depend upon how the Justices react to cases already on their docket or soon to arrive….
The decision technically did not go beyond the specific Arizona law at issue but, between the lines, seemed to have some broader themes. There was even a hint that Arizona’s more controversial alien control law — now widely known as “S.B. 1070″ — may not fare as well as its worker control law now has, particularly its provision that gives police wide authority to arrest and detain any individual that an officer believes is an unlawful alien. Arizona is preparing to file a new appeal, probably during the summer, to try to revive S.B. 1070 after key provisions were blocked in April by the Ninth Circuit Court.
In other words, it’s not clear how much this reflects a willingness to allow states to act on immigration matters, but it is a sign that the majority on the court are willing to allow states to go somewhat beyond minimal federal requirements, at least so long as not in conflict with federal law.