Sort of a surprise, but probably should not be considering the low esteem in which state sovereignty is held these days. The Arizona law is identical to federal law, so this Bill Clinton appointed has confirmed the mercurial whims of the ruling class trump the rule of law.
Expect further proceedings, but not so much a different outcome unless an appeal reaches the SCOTUS. Maybe not then, either. It will likely depend on whether Anthony Kennedy is feeling like the center of the universe that day.
Meanwhile, foreign lawbreakers are being favored over Arizona citizens by our government. Weir and illogical, but true. Illegal immigrants are allowed to run free in the United States because the feeds have decided enforcing its own laws is racist.
Touchy feely, "enlightened" government, anyone?