You are correct in that CA does not have a "Stop and Identify" law but police in CA do have the right to detain anyone during the course of an investigation (for example stopping someone after they receive a call from dispatch about a suspected thief in the area) and they have the ability to charge people with hindering an investigation if they are not cooperative in the course of this questioning which can include refusing to identify yourself.
The Supreme Court says that identifying yourself means verbally stating your name. Even if California does have such a statute--thus far no evidence of this law's existence has been presented--it does not and cannot require a person to carry and present written identification.
You've obviously never been through a Border Patrol checkpoint. Hell, the Feds don't even require "reasonable suspicion" to demand every ID from every passenger in any vehicle; and their jurisdiction stretches across the entire country, not just at the border.
Could you please point out exactly how/where the AZ law differs from existing Federal statutes?
According to the ACLU,
US citizens are not required to prove their citizenship at Border Patrol checkpoints. This is also consistent with my experience when I was in Arizona and Nevada in 2008; I respectfully declined to provide ID as I was only a passenger in the car, and we were simply waved through. The officers at the Hoover Dam highway checkpoint didn't even ask for it, though I'm not sure if they were Border Patrol.
In any case, it's largely irrelevant because the courts have ruled that immigration and DUI checkpoints are special situations in which violating certain civil rights is acceptable. On the other hand, the Arizona law applies everywhere in the state and targets people who may be walking or may even be in their own homes. Even if we assume that the feds can require identification at their checkpoints, that's still a far cry from enforcing the same requirement
everywhere.
Of course, I also think the checkpoints are a load of garbage and that
Sitz is among the worst SCOTUS decisions in recent memory. Luckily, my state's Constitution and Supreme Court prohibit suspicionless checkpoints, so at least I don't have to deal with that nonsense.