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 prevailed 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. …

Beyond being logically ridiculous — if a state law is unconstitutional because it’s out of sync with the federal government’s current priorities, does it become constitutional again when federal policy changes? — this argument is “an astounding assertion of federal executive power,” writes Justice Samuel Alito in a concurrence. The Obama Justice Department is suggesting that “a state law may be pre-empted, not because it conflicts with a federal statute or regulation, but because it is inconsistent with a federal agency’s current enforcement priorities. Those priorities, however, are not law. They are nothing more than agency policy.”

And there’s the rub: the Obama administration’s inability to distinguish policy from law. This becomes particularly perverse regarding immigration when, as Justice Antonin Scalia points out, what the administration delicately calls its priorities is quite simply a determination not to enforce the law as passed.