First, never said it was the only reason it was being challenged. Just said this is the reason why I think it will be found unconstitutional. Second, I said I think the due process issue is more important than the protected class. There are private groups and individuals that filed suit as well. You are referencing only the Justice Department's suit.
I only cited to the opinion regarding the claims from the U.S., but if you've read or kept up with the private claims, the same premise still stands: federal preemption is the focus. The
opinion by Judge Blackburn for the private suit dismissed most of the non-preemption claims as unlikely to succeed.
Virtually every private claim features a challenge to the law based upon federal preemption. Yes, several of them include other claims, ranging from the Confrontation Clause (dismissed as not likely to succeed) to the First Amendment (dismissed due to the fact that the code section in question was already deemed likely to be unconstitutional based upon preemption).
But most of the claims that were not preemption claims were dismissed as unlikely to succeed, or not ripe for review. Claims involving searches and seizures in violation of the Fourth Amendment can not be carried forth until the law is applied and improper searches occur; you can't judge whether a statute will be applied improperly based upon its face alone.
The only non-preemption claim I can find that the court considered worthwhile was a Compulsory Process claim. Essentially, one section of this law dictates that courts can only consider the federal government's verification when determining if an alien is lawfully present. This effectively prevents the defendant from introducing anything in his own defense.
Other than that, the primary point of contention is federal preemption. I only bring this up because there seems to be a lot of misguided conversations about whether illegal immigrants have constitutional rights, whether racial profiling is unconstitutional, etc. Ultimately, all of this is moot, as it has either already been dismissed by Judge Blackburn as not having a likelihood of success on the merits, or it was never even brought up in the lawsuits in the first place. I just think people are jumping the gun and making assumptions about what this case is focusing upon.