I was not going to comment. I am former Border Patrol, now retired.
But solsprack has it correct.
There has never been more than one checkpoint along I-10 in Texas that had the functional equivalency of a border crossing checkpoint. And that was the I-10 checkpoint at Sierra Blanca, Texas, east of El Paso.
Functional equivalency means that through pattern/practice of the Border Patrol, traffic surveys and court cases, the checkpoint at Sierra Blanca has demonstrated the percentage of its vehicle traffic that comes directly from Mexico, in this case. Through such a long time period as it has been in existence, Sierra Blanca, through the aforementioned facts, has demonstrated it is in fact exactly in the same situation as any of the river crossing ports of entry at say El Paso or McAllen, etc.
So that gives Sierra Blanca the search authority for vehicles.
BUT, there are no other locations in Texas along I-10 that have such authority.
Repeat, there are no other checkpoint locations along I-10 in Texas that have such blanket authority to search vehicles.
So if one does encounter such a checkpoint at some other location along I-10, then those authorities at that location MUST have indisputable facts BEFORE they can search your vehicle. Things such as the building blocks of law enforcement work, reasonable suspicion leading to probable cause. A drug dog alerting on your vehicle would be one of those facts. There are many more that could be used. These facts are ascertained by the trained observers most all professional law enforcement officers need to become. Things that most in the general population never see or notice are caught by these officers. Meaning things such as eye contact, occupants behavior, things most do not see, but as a law enforcement officer, things that set off alerts to odd, possibly criminal behavior of some sort.
So indeed, know your rights. Know what the Constitution offers you in protection.
But also know these same officers have rules they also must follow.