Here's the thing , from a practical point of view if the law is upheld look at it like this. Each time Law Enforcement comes across someone that is suspected as being illegal, then the contact is made with Federal authorities. If ICE, refuses to pick them up , or states, let them go, or we don't have the time, then eventually as most of the agencies here in Arizona's funds are already stretched to the limit they will eventually stop enforcing it in several locations. Further, SB-1070 much like a whole host of other laws passed by our state legislature based on unrealistic and not practical views will end up costing the state more money to enforce it. If for example as in the case with Sheriff Joe local Law enforcement detains someone after they have been told by ICE we are not going to pick them up, then that gives rise to another issue with unlawfully detaining an individual. Personally I cannot see how Arizona can make it a misdemeanor to be here illegally subject to Arizona Law with state punishment involved when that clearly is a violation of the Supremacy Clause.
A. IN ADDITION TO ANY VIOLATION OF FEDERAL LAW, A PERSON IS GUILTY OF
43 TRESPASSING IF THE PERSON IS BOTH:
2. IN VIOLATION OF 8 UNITED STATES CODE SECTION 1304(e) OR 1306(a).
http://www.azleg.gov/legtext/49leg/2r/bills/sb1070s.pdf
It would seem to me that in so doing the state of Arizona in that case there are little over-stepping their bounds as it provides for remedies for violations of Federal Law.
It doesn't matter however, from a practical standpoint this law depends on ICE willingness to take on the burden of accepting each of the people they arrest and as ICE is stretched thin enough already and with little invetment coming then it all becomes mute other than say perhaps something for a few in the State House to pound their chests over. I would say this though. with the changing demographics in our state, our officials should be careful what they wish for because sooner rather than later I would rather imagine SB-1070 will be a thing of the past.