Though overshadowed by the shocking Supreme Court decision on health care, the court’s Arizona immigration decision, issued three days earlier, remains far more significant than appreciated. It was generally viewed as mixed or ambiguous because the Justice Department succeeded in striking down three of the law’s provisions. However, regarding the law’s central and most controversial element — requiring officers to inquire into the immigration status of anyone picked up for some other violation — the ruling was definitive, indeed unanimous.

No liberal-conservative divide here. Not a single justice found merit in the administration’s claim that this “show me your papers” provision constituted an impermissible pre-emption of federal authority.

On what grounds unconstitutional? Presumably because state officials would be asking about the immigration status of all, rather than adhering to the federal enforcement priorities regarding which illegal aliens would not be subject to deportation.