The disadvantages of the law are clear--the perception is that law enforcement now has a legal bully club with which to beat and oppress an already beleaguered minority group. Every disadvantage, at least in popular thought, is connected to that concept. In fact, though, the way I understand it the Arizona law simply ensures enforcement of existing law. That should never really be a bad thing; if it is, it's probably the law's fault. And that's where we arrive, it seems to me. We have a law which the bulk of the country--those who are not particularly affected by the issue in any meaningful or significant way--is not particularly interested in enforcing. Those most impacted want to enforce it and doing so makes them look like bullies and aggressors. It's a vicious cycle of sorts, for sure.
The previous thoughts were strong. I think that the idea of increasing the power of the law enforcement officials to curb illegal immigration is something that will win favor with those who see illegal immigration as a major problem. The overwhelming advantage is that "something will be done." This cannot be denied in that there has been an absence of leadership on the issue and this is a start of, hopefully, developing this process. The racial profiling argument is a very persuasive one against the law. Another argument against it is that, to an extent, the law violates the spirit of federalism. This principle argues that federal and state governments work together in a spirit of cooperation and one does not overwhelm the other. When the issue of national border protection arises, this becomes an issue for the federal government. For example, if illegal immigration is stopped in Arizona, but the same law is not in California or Texas, immigration illegally could very well increase in those areas. The state of Arizona can only worry about itself, which is why the law does test the envelope of federalism because it seeks to solve a national problem only in its own jurisdiction. The problem will still exist, but "not in my backyard." This NIMBY approach has never bode well for national problems and national concerns. Another disadvantage is that the law does go against the fundamental spirit of America's belief of immigration. If legal immigrants who match the profile of those who are illegal are stopped and "must produce papers," this is about as far from the American ideal of immigration that one can get. The idea that "illegal immigration" has only one face is something that takes away from both American jurisprudence and American ethos.
I think that there are two possible advantages to this law. First, it might actually help to reduce illegal immigration. This is presumably a good thing because it would help the US be able to control how many people are in the country and to know who those people are. Second, it might make the general public's anger decrease -- they might be happier once there seems to be less breaking of the law.
I think the major disadvantage of the law is that it will promote racial profiling, no matter if the law officially prohibits that. If the police are supposed to check on people who look like they might be illegal, the police are going to check on people who are not white. This makes sense because most illegals aren't white, but it still means that the police will be treating people differently on the basis of race or ethnicity and that's not good.