I am fully in favor of the Arizona law. It is basically giving the state and local law enforcement the right to uphold national immigration law. It explicitly states in the law that A) the person required to show proof of citizenship must be stopped by law enforcement for some other reason and B) that it is illegal for enforcement to racially profile! Numerous times in the Arizona law it refers back to the federal law that it is based on. If a person is caught without proper proof, they are referred to federal agents to determine the actual legal status of the person in question. For other crimes it is no issue if a state wants to aid federal law enforcement uphold federal laws. The problem is that there are scare mongers that try to make the law be about race where in fact it is only about whether people are breaking federal laws and allowing the state to enforce those federal laws.
If the idiots up in DC end up making the Arizona law, then I guess they will in effect nullify other state laws that are designed to aid federal enforcement. Goodbye Amber Alert; only the FBI will be able to stop and detain drivers thought to be involved with kidnapping. After all, kidnapping is a federal offense and we can't allow state law enforcement to handle those type of offenses...
If a person comes here illegally -- no visa, no citizenship, etc. -- they are breaking the law. There is also a higher likelihood that that illegal person will break other laws: they may commit fraud by assuming a different person's identity, driving without a license, working undocumented to the IRS, voting as a non-citizen, etc. (not to mention more heinous crimes like drug trafficking, terroristic attacks, human / sex-slave trafficking, theft, assault, etc.). I have a friend whose identity was stolen by an illegal alien, and he didn't find out about it until he was pulled over and found there was a litany of arrest warrants out for "him" including driving without license and insurance, failure to appear in court, etc. It took him several months and hundreds of dollars in legal fees to restore his identity and clear his legal record (it helped that the assumed identity gathered those charges in a different state, so he was able to show proof that because he was living and working as a responsible citizen in one state, he'd be unable to commit those other crimes in that different state that held those warrants).
We are a nation governed by the rule of law. Everyone -- be they a homeless person at a soup kitchen or the president of the US; black, white, hispanic, or Asian -- is all held to the same standards under the law (thus the reason why Lady Justice is blindfolded). When we allow a segment of the population living in this country to be outside of the laws, we have as a result broken this very fundamental tenant of our nation. When we start removing the blindfold of justice, we actually begin to run the risk of holding other people in society held to different standards. If fraud committed by an illegal immigrant is overlooked, then who's to say we shouldn't also overlook some scam artist committing fraud too.
If there are too many obstacles to becoming legal residents, then there are legal channels to rectify the situation. Perhaps we need to create different types of visas, like a worker visa that would allow migrant workers to legally enter into the US to work during part of the year and return to Mexico (or Canada) during the down period. Or perhaps a family visa that allows family members to freely visit other members of the family that are legal residents. I'm all in favor of allowing people to come to this great country of ours. But in turn we need to have everyone respect the basic principles that made this country great: freedom in our lives under a common rule of law.