Please show me anywhere on this thread where I have said that I think the charges against the two men as claimed by the Texas Rangers are accurate. I am debating your contention regarding the underlying law in Texas that you have the right as a private citizen to detain someone for simple trespass and search them, and that this somehow does not constitute citizens arrest. If you tried this on someone on the street, the law would consider it to be an arrest and possibly assault.
Don't get me wrong, I think the law SHOULD allow you to do this. But the point is, it doesn't unless the trespass escalates to a felony level, typically when an illegal breaks into a structure and starts removing belongings - I think it is a legally risky tactic for the border groups to confront potential illegals, stop them and search them for simple trespass.