[Kevin]

I heard Erwin Chemerinsky is of the opinion that the feds will win this one. I tend to agree. I can see good arguments on both sides. Here are a few good ones off the top of my head:

1) The power to legislate in the area of immigration is a power delegated to the federal government. Much like the dormant commerce clause keeps states from enacting their own legislation relating to interstate commerce, the immigration powers of the federal government foreclose states even enacting completely consistent legislation.

2) Even if the states can arguably enact completely consistent legislation, if it's not enforced in the same way the feds enforce it, they are violating congressional intent. In this case, Arizona's intent seems to be to enforce this law much more effectively and broadly than any federal agency does. Congress' intent seems to be that by a conduct of lack of action and funding in the area, that they really don't want to block all illegal immigration, thus a policy actually doing that would be unconstitutional and preempted.

3) (and this is slightly weaker)That Arizona, by doing this has caused an international incident and is in effect conducting foreign policy, which it is not, as a state, allowed to do.