I am prepared to proceed slowly with this. The constitution of the State of Texas states: "The people shall be secure in their persons, houses, papers and possessions, from all unreasonable seizures or searches, and no warrant to search any place, or to seize any person or thing, shall issue without describing them as near as may be, nor without probable cause, supported by oath or affirmation." Of important note is the second word. It does not specify "citizen".
http://www.capitol.state.tx.us/txconst/sections/cn000100-000900.html
We even go a little further: No person shall ever be imprisoned for debt.
http://www.capitol.state.tx.us/txconst/sections/cn000100-001800.html
This is the real kicker: All free men, when they form a social compact, have equal rights, and no man, or set of men, is entitled to exclusive separate public emoluments, or privileges, but in consideration of public services.
http://www.capitol.state.tx.us/txconst/sections/cn000100-000300.html
And of course the starter: Texas is a free and independent State, subject only to the Constitution of the United States, and the maintenance of our free institutions and the perpetuity of the Union depend upon the preservation of the right of local self-government, unimpaired to all the States.
http://www.capitol.state.tx.us/txconst/sections/cn000100-000100.html
It is obvious that there are no provisions for state or federal government to detain people without oath or affirmation, much less a warrant. Please clarify the exact circumstances that create an illegal person.
I have no idea why you are posting Texas law or any other law for that matter to me, I am not a lawyer in Texas or anywhere else and I haven't even stayed at a Holiday Inn Express recently.
I do know the US Border Patrol regularly stops people walking and driving in my area and apprehends many for being in this country illegally. At times they fill buses with them. I also know the Border Patrol in this area does traffic stops and apprehends illegals, as well as having fixed checkpoints on the major highways along the border. They also hold impromptu checkpoints along the traveled roads in this area with other LE agencies.
I cannot tell you what authority they use to do this, nor do I care. If you are so concerned about LE authority to require ID or apprehend illegal border crossers I suggest you take it up with the appropriate agency. Or you could simply wander around near the border and when asked to produce ID, you can refuse to. I imagine if you do that you will find out whether they have the authority to do so or not. I just cooperate when stopped by any type of LE, and I don't even want to know what happens if I choose not to. If I ever feel the urge to not cooperate I am sure I will find out then.