I certainly agree, but would like to focus on what I see as a more fundamental violation of the Constitution in this new law. It violates the 14th Amendment to our Constitution, which begins
Section 1. All persons born or naturalized in the United States, and subject to the jurisdiction thereof, are citizens of the United States and of the State wherein they reside. No State shall make or enforce any law which shall abridge the privileges or immunities of citizens of the United States; nor shall any State deprive any person of life, liberty, or property, without due process of law; nor deny to any person within its jurisdiction the equal protection of the laws.
The new Arizona law is intended to identify illegal aliens. But on the basis of "reasonable suspicion," an officer could pull over and demand papers from an American citizen, simply because he or she looked like the officer's expectations of an illegal alien. (*Note added 1 May 2010: The same applies to the amended law - see discussion in comments below, and my podcast on this topic.) More specifically, someone who has dark hair and a mustache (as I proudly do) would be more likely to be stopped by a cop in Arizona, under this law, than a clean shaven guy with blond hair and blue eyes. That seems to me to be ipso facto a violation of the equal protection provision of the 14th Amendment.
Now, police stop people who may look like suspects all the time. If there's a description of a serial killer, which unfortunately happens to look like me, I think it's entirely appropriate that I be stopped and questioned (hey, I watch Criminal Minds). But that's a very specific situation, and unlike what the Arizona Immigration Law does, which singles out a whole class of people, who happen to look like whatever the Arizona police might envision an illegal alien to look like.
I hope this law is struck down as soon as possible, as the unconstitutional, un-American piece of state legislation it is.
10-min podcast discussion of this issue, with consideration of the amended law, and a response to Chris Matthews