And after reading the Order, I think the Court's finding that "Even though Arizona’s interests may be consistent with those of the federal government, it is not in the public interest for Arizona to enforce preempted laws" hits the nail on the head.
We are all concerned about the effects of illegal immigration to the United States. Arizona's concerns about border violence and the drug trade are real concerns. However, it is hard to deny that the issue has become so politicized that it has obscured the facts.
But however strongly we feel about illegal immigration, allowing one state (or 5, or 22) to enforce a fundamentally federal policy like immigration is simply not a good idea. We have a federal system for a reason. We can go on about state's rights but immigration is a uniquely federal issue, and it is important that the federal government be primarily responsible for administering it. The body of law is very complex - we lawyers will be the first to tell you there are a lot of shades of "illegal" - and it is simply impossible to train state law enforcement agents on the legal minutiae of what it means to be "in status" or "in a period of stay authorized by the Attorney General" or "prima facie eligible for relief." We already have a system for determining who gets to stay and who has to leave, and it can take several rounds of legal briefing to definitively say one way or another what the law says.
Leave the job to those who have been doing it. Yes, we need change in that system, but the solution to the federal immigration policy's problems is not to hatch fifty different state policies.