I heard Brit Hume over on Fox the other day questioning whether there was anything wrong with the new Juan Crow law in Arizona. Hume emphasized the point that citizens would only be asked for their papers during normal police contact, i.e. if the police had already stopped you for something else. In the course of that stop police could ask you for your papers if "REASONABLE SUSPICION EXISTS THAT THE PERSON IS AN ALIEN."
As reprehensible as the proposition of being asked to prove your citizenship is, consider that in Arizona police roadblocks are perfectly legal, and conducted routinely and incessantly. I've been through quite a few of them myself. In each case the officer looked over me, my passengers, and our car, and waved us through. Is there anything more subjective than that?
By this method EVERY driver and car has the potential, indeed likelihood, of normal police contact. In this context Arizona really is a police state, and the new law looks like an attempt to identify and deport or jail every undocumented immigrant.
Although the US Supreme Court has ruled roadblocks constitutional, the Minnesota state supreme court ruled that our constitution is more protective of individual rights than the federal one, and that roadblocks are NOT permissible here.