I travel the both the I-8/I-10 and the I/10/I-17/I-40 route thru AriDzona annually.
This particular SC decision, for better or worse, will have no bearing on how the US Dept of Homeland Security decides to run their east-west “checkpoints” on I-8/I-10 in CA/AZ. They ask EVERYONE in the vehicle (who is old enough to speak) to state their citizenship. They also have the right of search and seizure (and even have makeshift “secondary” sections set up off-road). I’ve seen a LOT of people people pulled over by USBP/Customs for document examination on these roads in the last 10+ years, even Asian people driving expensive cars. I don’t carry papers but have always been let go (one time after a cursory search of a trailer).
The days of a passenger with bare feet hanging out the window (no A/C in cars) and loading the bed of one’s pickup with kids and a giant thermos to head interstate to grandma’s house are gone :=[