Law Professor Kris Kobach has an Op-Ed in the New York Times, explaining the truth about the new Arizona law.[Why Arizona Drew a Line, April 29, 2010] It's good that they let him publish this, because you aren't going to see a lot of this in either the NYT editorial page or their news reporting. He has the answers to five  bogus claims that opponents of the bill make:

• It is unfair to demand that aliens carry their documents with them.
• “Reasonable suspicion” is a meaningless term that will permit police misconduct.
• The law will allow police to engage in racial profiling.
• It is unfair to demand that people carry a driver’s license.
• State governments aren’t allowed to get involved in immigration, which is a federal matter.

You can read the answers in detail on the New York Times website, but I thought I'd mention the part about documented immigrants being expected to keep their documents handy. Kobach reminds us that "[S]ince 1940, it has been a federal crime for aliens to fail to keep such registration documents with them."

That is, if you're a foreigner in the US legally, whether on a Green Card, a visa, or a passport from a non-visa country like Canada, you're responsible for proving it. Why is that so hard?