A temporary injunction has halted the most useful parts of Arizona's law. The injunction, courtesy Legal Insurrection, notes that:
Thus, an increase in the number of requests for determinations of immigration status, such as is likely to result from the mandatory requirement that Arizona law enforcement officials and agencies check the immigration status of any person who is arrested, will divert resources from the federal government’s other responsibilities and priorities.
Riiiiight.
Free healthcare, prescription drugs for all, and an increasingly bureaucratized education system—a mere handful of the priorities that she must be thinking of—appear not once within the literal text of the Constitution.
Defending the country, ensuring everyone's equal right to vote, and now apparently enforcing our immigration laws are "priorities" which we can apparently afford to do without, however.
Even though the Constitution lays them out as the Federal government's explicit responsibilities.
So goes the upside down world we're forced to inhabit.
See-Also: Gateway Pundit, Ace of Spades, Michelle Malkin.
That speculation about resources and enforcement priorities in her decision just isn't law.
How does the AZ law preempt Federal law? I don't know because it's not in the decision. the decision seems to be about enforcement and resources, not law.