Whoops, wrong state. My bad.
The relevant statute in Arizona is:
A.R.S. S 13-1303 wrote:
A. A person commits unlawful imprisonment by knowingly restraining another person.
B. In any prosecution for unlawful imprisonment, it is a defense that:
1. The restraint was accomplished by a peace officer acting in good faith in the lawful performance of his duty; or
2. The defendant is a relative of the person restrained and the defendant's sole intent is to assume lawful custody of that person and the restraint was accomplished without physical injury.
C. Unlawful imprisonment is a class 6 felony unless the victim is released voluntarily by the defendant without physical injury in a safe place prior to arrest in which case it is a class 1 misdemeanor.
So it's still a crime in Arizona, it's just "unlawful imprisonment" instead of "kidnapping." Perhaps with respect to "facts selectively chosen to back up your argument," people who live in glass houses shouldn't throw stones.
You raise some other good points.
On the citizens arrest issue: I honestly have no idea how citizens arrests work. The extent to which we talked about them in law school was "don't do it, as you are very likely to fuck it up and thereafter lose a lawsuit," and that's all I know. It is possible that what this guy did was a valid citizens arrest, and, if so, he'd have a valid defense in court. However, if the facts alleged are true-- if he threatened to shoot them, threatened to have his dog attack them, let along striking one of them-- it's almost certainly not a legitimate citizens arrest, but I don't know enough about the issue to say for sure. Maybe one of the other lawyers on the boards knows better than I.
As to the proper course of action... I don't know, it's tough. But I'd like to stress that there's no allegation that THESE particular illegal immigrants broke into his house, stole his cars, left trash in his yard, etc. I know that many illegal immigrants have done these things on his property, but illegal immigrants are individuals, not a collective, and you can't legitimately punish one group of them for the sins of the others.
Are they foreign invaders? No. They're foreign aliens. I would assume that invading requires some kind of hostile or aggressive or violent or warlike intent or behavior. Anyone who'd like would be welcome to try this defense in court, but I'm pretty skeptical that it'd work.
What would I have done if I were this guy? Probably consulted with local police and a good lawyer to figure out what my legal options are. It's possible that he has some good legal options; it's possible that he doesn't. If he doesn't, then I would be pretty pissed if I were in his situation. I empathize with what he did, and it's possible that I might have done something similar in the same situation. My point is simply that his behavior being UNDERSTANDABLE does not make it LEGAL. In the exact same way that what illegal immigrants are doing is UNDERSTANDABLE-- most are trying to escape poverty, provide for their families, build a better life-- but that doesn't make it LEGAL. And Kilmoll has been hanging his hat on the importance of legality.